I think the problem is the graphics driver, but when I try to install the latest version from the ati site you directed me to, the install wizard says my graphics adapter is not supported, however Sony (I have a vaio) does not offer graphics updates…
Seem to have the same problem, except I have only recently bought the game, and the crash kills steam as well. This happens with no other game, so I do not think that it is a steam problem.