It seems that Fallout 3 does not handle being run on a processor with more than 2 cores, which leads to random freezing.
Fix: Edit the fallout.ini file in “C:Users(your name)DocumentsMy GamesFallout 3” (Windows 7 and above)
[General] section, locate the
bUseThreadedAI=0 line and change it to
Below that, add
Save the file and restart Fallout 3.
Note that if you’re having issues where Fallout crashes after starting a new game, it’s most likely due to incompatible video hardware, most notably trying to run it with Intel-based graphics.