Hearthfire contains a deleted NavMesh in Breezehome, which means that a great deal of mods that are editing Breezehome's NavMesh (example: Unofficial Skyrim Patch) are going to cause CTDs if you try to enter the house with them enabled.

Normally, I don't advocate fixing these sorts of bugs, but because of Hearthfire's shenanigans Breezehome is now pretty much unsafe to modify in its entirety unless your mod is mastered to Hearthfire (which is currently impossible due to unrecognized sub-records in the ESM). This is a severe incompatibility given the number of mods out there that do edit the house, and it is not known at this point if the conflict can actually be fixed (removing NavMesh Forms in the CK can result in the CK crashing trying to save the mod).

So in essence, the modders are pretty much helpless on this one. If Bethesda does not fix this (which they likely won't), let this serve as a precaution: if you are crashing trying to enter Breezehome, make sure ALL mods that modify that home are disabled.

My manor is almost done, and all I need from Breezehome is my wife. After that, I doubt I will even set foot in Breezehome again, should I reactivate USKP after I am done with anything related to Breezehome?

Should be fine. Just don't load any mods editing Breezehome if you want access.

Sounds good. At least the conflict is just Breezehome.

Hopefully....

Specifically, so far anyway, navmesh form ID 000CB4F3 is the one that was deleted. I suspect it's the little island that's next to Lydia's bed since it had two isolated triangles and someone probably tried to fix it without realizing the damage done by deleting a navmesh.

I have the Breezehome ctd, and I have no mods changing the house. Plenty other mods, but none which directly affect the house (other than the Lydia-loop-fix, which I have disabled).

I have loads of stuff stored in there, and it is my main house! What could be causing it?

Edit: Ok, I worked it out: Better Dynamic Shadows gets rid of the shadow-striping thing in Breezehome, and was causing ctd. Shame - now I have borked shadows again
Also I guess Lydia-Loop-Fix may cause similar issues, though I got rid of that as soon as I ctd'd so I can't be sure...

Just another update: Another confirmed deleted NavMesh exists in Wilderness cell (-3, -17). This cell is notably modified by Scenic Carriages, and as such will cause CTDs if you have it installed and get close to Lakeview Manor's build site.

So I bought Hearthfire.....just to have it potentially nuke my game?

This really sounds like Bethesda just said "To hell with it. Don't care what it could potentially mess up, make it work and release it anyway."

I believe they did more than just deleting 2 navmesh triangles. Take a look at the alchemy lab area:

http://imageshack.us/a/img141/8162/creationkit201210052308.jpg

http://imageshack.us/a/img593/8966/creationkit201210052311.jpg

As you see, they also added a single bed, a target dummy and a container. Currently checking if they're supposed to be disabled after the house has been furnished -although I doubt it.


UPDATE: They're part of the adoption additions. All the player houses in the main cities, have been modified for this purpose. Apparently, should the player chooses to adopt and send the children to live in any of these houses, certain furniture will be disabled and in at least one case (Hjerim) areas will be expanded, to accommodate the additional inhabitants.

So, the Breezehome CTD wasn't triggered by anyone running the XBOX360? Otherwise, I'd really have expected that bug to be fixed in time for the PC release.

How would people using the 360 have mods that modify Breezehome? The problem is caused by mods altering Breezehome not playing nicely with Hearthfire.

Yes, those additions are WHY they altered the navmeshes and unfortunately why one of them ended up deleted. They probably said "hey, two island triangles, merge these" and didn't realize what it would do.

breezehome is totally off limits to me now, i have the alchemy lab fix and even when i disable it the game still ctd's. i'v really tried everything to get it to work but nothing.

i'm not sure if even disabling some of these mods will work, it's completely screwed for me now.

From what I understand, Hearthfire may have actually fixed the Dawnguard Breezeholm alchemy bug [which, to me, implies that the bug occurred because something from Hearthfire got added to Dawnguard by mistake].

[ edit / add ]
More specifically at note, it's rough, since it necessitated a few problems. More specifically, if you list your mods it may be easier for others to ID. However, I will save some time and mention that UKSP will cause CTDs w/ Hearthfire installed.

More Dynamic Shadows also CTDs on entering Breezehome with Hearthfire installed, but I attribute that more to the plugin bursting at the seams with deleted Refs than anything else.

Open Cities will cause the same until I've packaged the next update. I've already fixed it on my end and it seems solid, though I'm obviously not happy with the solution since it leaves a giant navmesh island in place due to Bethesda's deletion.

this is the mod http://steamcommunity.com/sharedfiles/filedetails/?id=88446940&searchtext=Dawnguard+Breezehome+Alchemy+Lab+Fix i was using, the only mod affecting breezehome. i tried everything i could think of to get around it, but in the end i just disabled hearthfire and reloaded an earlier save so i could get everything of value out of breezehome before enabling it again, knowing those doors were going to remain forever closed.

i didn't know about USKP being uncompatable, i'll disable that too and see if it sorts out some of the other bugs. hearthfire has been a mess for me so far, the breezehome ctd just being one issue of many.

ok so i finally realised it was the USKP causing the crash, that's a relief, it saved me a hell of a lot of backtracking.

There is a newly released beta patch for the USKP that removes any fixes regarding Breezehome and allows you to run both the USKP and Hearthfire without issue.