One last thing I can think of to try. Do you have the latest version of FOMM (if you use it that is)? Someone else had a similar situation as you, and once they updated it, they game loaded up again.
Interestingly enough, FOMM was updated yesterday when you posted this. I updated it, but I still have the issue. Thanks for the heads up though, heh.
another thing to try: delete your fallout.ini file to have the game recreate a new one for you. you may have bad ini settings that are crashing the game.
I'll try this in a moment then get back to you.
EDIT: Still nothing
Also make sure you haven't accidently deleted the contents of any of the default folders that are in the Data folder eg. Menu
Looked through the recycling bin, nothing from the data folder.
Doesn't xCalibr need Calibr installed first?
Yes, and it is. CALIBR.esm is right up there at the top
EDIT
Strange.. I just disabled all my mods again except for the DLC and Fallout3.esm (which I've already tried doing multiple times with no results) and loaded up GameBooster (I always use it before I play Fallout) and then tried again, and it worked fine. Loaded up as normal.
I just don't understand how it could be a mod thats causing this, because I didn't install any new mods between the time it last worked and the time it stopped working. I didn't even change my load order in that period of time.
EDIT 2
So I went back through and kept all the main "overhaul" mods this time. WMK, MMM, FWE, and the compatibility patches and Mez's merged patch. I loaded the game up and the menu didn't load just like before. I don't see how this could be caused by one of these mods, they all worked completely fine before.
EDIT 3
I went back through and activated everything I was using that WASN'T related to WMK/MMM/FWE and it worked fine. So I guess I've narrowed it down to one of those overhauls. Which, again, doesn't make sense. They all worked fine together before.
EDIT 4
So many edits, jeez. But this time I used my normal load order, except I left out WMK and MMM and the merged patch. Everything worked fine. So its not FWE then.
EDIT 5
Aha! Looks like something from WMK is causing the problem. Once more, I still don't get it though, because it worked fine before now. Guess I'll do some more investigating and see if I'm missing anything WMK-related.