SO, I'm having an issue with existing NPCs not properly using new or relocated idle markers. When testing it, everything works fine if I'm using a new game save - I travel around, every one is in good working order, no problems. When I load an advanced save (where towns have already been discovered) the NPCs start behaving ... oddly. Sometimes they just stand around, or they'll use idles for a couple mins and then just stop dead. If I recycleactor and re-load they work properly again, but I suspect that asking everyone to do this to every NPC they encounter would not be well received lol.

So.. any idea what might be causing this for non-new games? or how I might fix it? Thanks in advance for any help!

This sounds like the Navamesh bug: http://www.gamesas.com/topic/1361767-navmesh-bugs-part-iii/page__fromsearch__1. If this thread describes some of your problems (which it appears to) then we are ALL! waiting for a fix.
Edit: After re-reading your post, are you talking about a mod you are using or just the game in general? If it is not a mod, then the above is not the issue and you should maybe check in the Tech problems forum.

Ahh yes, navmesh bug. I had heard a rumor that it had been resolved and I guess optimism got the best of me. I will check out the link, thanks!

And yes, the problem is with a mod, not the game itself.

I just wasn't sure if this was navmesh related because it doesn't seem to be a reading old navmesh vs. new navmesh or losing navmesh entirely type of thing. They CAN navigate - they just choose not to sometimes lol. It only starts to have issues when loading old saves, something is getting messed up when re-visiting towns as opposed to discovering them for the first time, on new games everything works fine.

The bug is erratic and differs....sometimes all the navamesh disappears and the npcs won't move or are all huddled together......other times, they can't get to markers...I've had them walking half in-out of statics or jumping from place to place for no apparent reason---even walking in air . Sometimes saving/reloading and re-entering a cell solves the issue temporarily. Part of the problem is leaving an area, going 2 cells away, and then returning. Hopefully they will have a fix soon...they are working on it, but the last fix caused CTD's so they pulled the fix.

well THAT'S encouraging... lol