Basically what the title says.

I was making my adventure, quest, dungeons. I decided after a few hours of work it was time to test it in Skyrim to see how it was going. Loading the data file on skyrim launch crashes the game just after the imperial emblem shows up, before the menu buttons do. Loading it in the creation kit, it get's to Loading References... and then hangs, eventually crashing.

Is my mod lost? Do I have to just start over being a little more wise this time?

EDIT: going back through the backups one by one, it seems the most recent working one is before I constructed my indoor dwemer dungeon. I didn't do anything except for lay out it's shape. Is there something about that that I did wrong, or just unlucky?

happens when the mod has dependencies not checked. such as it takes resources from another mod plugin addson etc and its not there. or it maybe something else.