Eurogamer recently had a Q&A session with the VP of Marketing for Bethesda, Pete Hines. In the interview, Pete was quoted as saying that a PC patch will be released later today that will fix several issues that PC users have been experiencing.
Updates:
The Fallout 3 PC patch will not be released today according to a Bethesda staff member. Instead, it will be released later this week. The patch also only addresses issues of the game crashing on exiting the game. Bethesda is "moving along with pulling together a more extensive update. We’re still in the process of going through and looking at any issues/fixes, and once that is done there is lots of additional testing/fixing that has to be done before it can be released. Similarly, we're looking into matters on Xbox 360 and PlayStation 3."