Try this. Go to My Documents\My Games\Fallout3 (or FalloutNV)
Open the Fallout.ini file, and find the line:
bUseThreadedAI=0
Change the 0 to a 1 like so, "bUseThreadedAI=1" (minus the speech marks of course). Add another line after it and copy and paste the line below:
iNumHWThreads=2
It should fix the freezing issue. This works at least for me.
I don't think they have, I know they've tried solutions but it has to be a core support issue since the engine doesn't seem to agree with four running at once. Thus, the solution above. If you're on PC at least. Used to crash all the time on PC for Fallout 3, yet never had the problem with New Vegas.