Hi folks, as the title says, I'm stuck in the citadel. I came there after the enclave attacked the purifier and i escaped with Dr. Li. Inside the citadel interior, everything works fine, but as soon as I try to get to the courtyard, the game freezes. It's the usual freeze with the sound playing on while the rest of the game doesnt react. I've got quite used to these freezes as I got at least on per hour played (about 30), sometimes every minute. But the big problem here is: I can't leave! This is the way it happened: Went out of the citadel interior to the courtyard: normal. leaving the citadel: freeze. After that, all saves within the last half hour will lead to a freeze when leaving the citadel interior. I loaded an earlier save (about 1 hour lost) and played and exactly the same happened. I also had this problem in Project Purity in the Waters of Life quest, there an older save fixed it.

My specs:
Fallout 3 GOTY - steam

AMD Phenom X4, ATI Radeon 5770, 8 GB RAM, VIA onboard sound

Fixes I tried:
The threadedAI and NumHWThreads-Fix
Tweaked cell-loading and memory management for >2GB RAM
Moved steam outside the program files
disabled antivirus
started with admin rights
disabled uac
coc to another place: game freezes except when moving to PPurity02 (the part of the Jefferson Memorial where the game freezed during waters of life), but leaving there will freeze

I am logged offline into GfWL (so unnecessary with steam already used) and did not type in the product code given by steam (worked either way), could this be the issue?

Any help will be appreciated!