for my surprise, the game ran perfectly well for the first hour and then started crashing to desktop everytime I approached the Super Duper Mart (or what ever its name is

I then read about several possible fixes like leaving your keybindings at standard which actually solved nothing. Finally, after reading about the possible codec problem, I used Codec Sniper to check if some codecs were broken, but they were all fine. Since I was using an old version of ffdshow, I decided to update it anyway because on my version I could not make exceptions for whether using ffdshow in a certain application or not. I got the latest version from here -> http://sourceforge.net/project/showfiles.php?group_id=173941&package_id=199416 , it was just released yesterday. That alone allowed me to actually go round the building, finding the entrance of the Super Duper Mart, note that I still have not added fallout3.exe to the exceptions lists. That was a major step forward for me since I can assure that this was no coincident because I never managed to get that far with the old version and I always get that far with the new version. Unfortunately, the game still crashs when entering the Mart after I added fallout3.exe as a exception in ffdshow. Which means I am free the run around the world but I cannot enter a building

That information does actually barely help us I guess but I thought I will let you know anyway.
Greets