Normally I wouldn't bother posting about this kind of problem but I just lost a few days worth of work over it. Someone tell me if you've experienced the same issue before:

Spent the past few days adding new objects and encounters to my mod http://skyrim.nexusmods.com/mods/25704, basically extra polish before I upload my 1.6 patch. Quest dialog is already done and - before you think it - no it's not the SEQ dialog bug. Quest dialog for WTDragonHunt is still functioning however on my test playthrough today I found that all dialog relating only to the WTBarrowOfTheWyrm quest to be missing. Not only that, but none of the quest markers pertaining to that quest are showing up. Again, other quests in my mod appear unaffected, only the dialog and markers pertaining to the WTBarrowOfTheWyrm quest were mysteriously broken.

I've already tried to regenerate the SEQ and repack into a new BSA however that doesn't fix the problem. I was able to solve it by rolling back to a backup save of the ESP file I took a few days ago and have been comparing changes made between the two files. Once again, no changes to any quests were made in that time frame, the only changes have been cosmetic, ie: object, enemy placement.

I have a fair idea what I changed over the past few days so putting those changes back in to the mod shouldn't be too difficult, but what I would like to understand is how such a serious problem occurred in the first place.

No dialog. No quest markers. Only affecting one quest. Any ideas?