Hearthfire seem to want to keep track of everything that leaves my inventory. Or maybe it is just specific items... Still, it seems excessive, as the items in question seem to have nothing to do with Hearthfire. This leads me to believe it is likely some sort of scripting typo, or perhaps the player getting assigned to a quest alias they shouldn't be?

I just discovered this repeatable CTD by purchasing ten or so spell tomes and clicking them rapidly in sequence to learn them all. Take a look at what Hearthfire is doing on every click, until it causes a CTD:

[10/25/2012 - 03:41:51PM] [BYOHHouseBuildingPlayerScript &--#60;alias Player on quest BYOHHouseBuilding (0300305D)&--#62;]OnItemRemoved [Form &--#60; (000A2711)&--#62;], itemCount=1[10/25/2012 - 03:41:51PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] UpdateLogCount[10/25/2012 - 03:41:51PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] logcount=3[10/25/2012 - 03:41:52PM] [BYOHHouseBuildingPlayerScript &--#60;alias Player on quest BYOHHouseBuilding (0300305D)&--#62;]OnItemRemoved [Form &--#60; (000FF7D1)&--#62;], itemCount=1[10/25/2012 - 03:41:52PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] UpdateLogCount[10/25/2012 - 03:41:52PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] logcount=3[10/25/2012 - 03:41:52PM] [BYOHHouseBuildingPlayerScript &--#60;alias Player on quest BYOHHouseBuilding (0300305D)&--#62;]OnItemRemoved [Form &--#60; (0009E2AD)&--#62;], itemCount=1[10/25/2012 - 03:41:52PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] UpdateLogCount[10/25/2012 - 03:41:52PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] logcount=3[10/25/2012 - 03:41:52PM] [BYOHHouseBuildingPlayerScript &--#60;alias Player on quest BYOHHouseBuilding (0300305D)&--#62;]OnItemRemoved [Form &--#60; (000A2712)&--#62;], itemCount=1[10/25/2012 - 03:41:52PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] UpdateLogCount[10/25/2012 - 03:41:52PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] logcount=3[10/25/2012 - 03:41:52PM] [BYOHHouseBuildingPlayerScript &--#60;alias Player on quest BYOHHouseBuilding (0300305D)&--#62;]OnItemRemoved [Form &--#60; (000A2714)&--#62;], itemCount=1[10/25/2012 - 03:41:52PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] UpdateLogCount[10/25/2012 - 03:41:52PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] logcount=3[10/25/2012 - 03:41:52PM] [BYOHHouseBuildingPlayerScript &--#60;alias Player on quest BYOHHouseBuilding (0300305D)&--#62;]OnItemRemoved [Form &--#60; (000A2715)&--#62;], itemCount=1[10/25/2012 - 03:41:52PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] UpdateLogCount[10/25/2012 - 03:41:53PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] logcount=3[10/25/2012 - 03:41:53PM] [BYOHHouseBuildingPlayerScript &--#60;alias Player on quest BYOHHouseBuilding (0300305D)&--#62;]OnItemRemoved [Form &--#60; (000A270F)&--#62;], itemCount=1[10/25/2012 - 03:41:53PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] UpdateLogCount[10/25/2012 - 03:41:53PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] logcount=3[10/25/2012 - 03:41:53PM] [BYOHHouseBuildingPlayerScript &--#60;alias Player on quest BYOHHouseBuilding (0300305D)&--#62;]OnItemRemoved [Form &--#60; (000A2717)&--#62;], itemCount=1[10/25/2012 - 03:41:53PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] UpdateLogCount[10/25/2012 - 03:41:53PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] logcount=3[10/25/2012 - 03:41:53PM] [BYOHHouseBuildingPlayerScript &--#60;alias Player on quest BYOHHouseBuilding (0300305D)&--#62;]OnItemRemoved [Form &--#60; (000A2713)&--#62;], itemCount=1[10/25/2012 - 03:41:53PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] UpdateLogCount[10/25/2012 - 03:41:53PM] [byohhousebuildingscript &--#60;BYOHHouseBuilding (0300305D)&--#62;] logcount=3

EDIT: After cleaning all my mods and running basically just the DLC's and unofficial patches, this definitely causes a CTD every time. I even went slow, clicking a tome, waiting a second, clicking the next, and after the third or forth, bam. Will just have to keep an eye out for the CK update.

More script weirdness from Hearthfire... I really hope Bethesda patches this because it's causing CTD's left and right. This time, I had just activated a dragon claw door (which you can see in the log at the start of the below code), followed by more of this inventory checking gobbledegook, which is particularly odd since I was actually in combat with a drougr lord and not looting anything at the time. Nevertheless, this resulted in yet another CTD. This is happening so often now it is nigh unplayable.

[10/25/2012 - 06:02:42PM] [byohhousebuildingscript ] UpdateLogCount[10/25/2012 - 06:02:42PM] [byohhousebuildingscript ] logcount=3[10/25/2012 - 06:03:52PM] error: Cannot call Activate() on a None object, aborting function callstack:    [ (000ED3FD)].HallofStoriesKeyholeScript.checkSuccess() - "HallofStoriesKeyholeScript.psc" Line 114    [ (000ED3FD)].HallofStoriesKeyholeScript.OnActivate() - "HallofStoriesKeyholeScript.psc" Line ?[10/25/2012 - 06:03:52PM] warning: Assigning None to a non-object variable named "::temp4"stack:    [ (000ED3FD)].HallofStoriesKeyholeScript.checkSuccess() - "HallofStoriesKeyholeScript.psc" Line 114    [ (000ED3FD)].HallofStoriesKeyholeScript.OnActivate() - "HallofStoriesKeyholeScript.psc" Line ?[10/25/2012 - 06:04:08PM] [BYOHHouseBuildingPlayerScript ]OnItemAdded [MiscObject < (0000000F)>], itemCount=12[10/25/2012 - 06:04:08PM] [byohhousebuildingscript ] UpdateLogCount[10/25/2012 - 06:04:08PM] [byohhousebuildingscript ] logcount=3[10/25/2012 - 06:04:20PM] [BYOHHouseBuildingPlayerScript ]OnItemAdded [MiscObject < (0000000F)>], itemCount=16[10/25/2012 - 06:04:20PM] [byohhousebuildingscript ] UpdateLogCount[10/25/2012 - 06:04:20PM] [byohhousebuildingscript ] logcount=3[10/25/2012 - 06:04:29PM] [BYOHHouseBuildingPlayerScript ]OnItemAdded [MiscObject < (0000000F)>], itemCount=7[10/25/2012 - 06:04:29PM] [byohhousebuildingscript ] UpdateLogCount[10/25/2012 - 06:04:29PM] [byohhousebuildingscript ] logcount=3[10/25/2012 - 06:04:30PM] [BYOHHouseBuildingPlayerScript ]OnItemAdded [Form < (00063B46)>], itemCount=1[10/25/2012 - 06:04:30PM] [byohhousebuildingscript ] UpdateLogCount[10/25/2012 - 06:04:30PM] [byohhousebuildingscript ] logcount=3[10/25/2012 - 06:04:57PM] [BYOHHouseBuildingPlayerScript ]OnItemRemoved [Armor < (0002D753)>], itemCount=1[10/25/2012 - 06:04:57PM] [byohhousebuildingscript ] UpdateLogCount[10/25/2012 - 06:04:57PM] [byohhousebuildingscript ] logcount=3[10/25/2012 - 06:04:59PM] [BYOHHouseBuildingPlayerScript ]OnItemRemoved [Armor < (0002D74F)>], itemCount=1[10/25/2012 - 06:04:59PM] [byohhousebuildingscript ] UpdateLogCount[10/25/2012 - 06:04:59PM] [byohhousebuildingscript ] logcount=3[10/25/2012 - 06:05:00PM] [BYOHHouseBuildingPlayerScript ]OnItemRemoved [Armor < (0002D75A)>], itemCount=1[10/25/2012 - 06:05:00PM] [byohhousebuildingscript ] UpdateLogCount[10/25/2012 - 06:05:00PM] [byohhousebuildingscript ] logcount=3[10/25/2012 - 06:05:01PM] [default2StateActivator < (000ED772)>] Closing[10/25/2012 - 06:05:16PM] [BYOHHouseBuildingPlayerScript ]OnItemRemoved [Form < (020176F4)>], itemCount=1[10/25/2012 - 06:05:16PM] [byohhousebuildingscript ] UpdateLogCount[10/25/2012 - 06:05:16PM] [byohhousebuildingscript ] logcount=3[10/25/2012 - 06:05:21PM] [BYOHHouseBuildingPlayerScript ]OnItemRemoved [Form < (020176F4)>], itemCount=1[10/25/2012 - 06:05:21PM] [byohhousebuildingscript ] UpdateLogCount[10/25/2012 - 06:05:21PM] [byohhousebuildingscript ] logcount=3

Afraid I'm just going to have to disable this awesome DLC until they patch out this code fumble. There is no logical reason a house building mod needs to run a script for every single item added to the player's inventory. >.<

I am curious to know what the consequence would be of doing "stopquest BYOHHouseBuilding" as a workaround. I tried this and avoided these repeatable CTD's in a recent test, with none of the above printouts to the log on inventory events. I then did "startquest BYOHHouseBuilding" and looted a bunch of stuff and the messages re-appeared. This leads me to wonder whether it would be safe, or if future quest events related to buying other houses (I only have the Falkreath house) would still work after re-enabling when I got around to them, so that my game is playable in the meantime.

Pretty good debugging so far.
Hopefully they will release the Hearthfire scripts soon for CK.

The next step, once this happens, might be to see if you can mod this quest and fix it in the CK.

Have you reported this issue to the Unofficial Hearthfire Patch http://www.gamesas.com/topic/1415111-unofficial-hearthfire-patch-thread-1/? If it is repeatable as you say then Arthmoor can probably fix it.

Edit: Well, you are probably better off reporting it to the http://bugzilla.darkcreations.org/describecomponents.cgi?product=Unofficial%20Skyrim%20Patch%20%28USKP%29, but it wouldn't hurt to post in the forum thread either.

Edit 2: Why in Oblivion does Hearthfire need to constantly check your inventory? Makes little sense.