I haven't done much checking to verify this, but apparently there is a bug in the ATI drivers for FBO which will crash when rendering to a cube map target. Since an envmap is a cube map, generating one can crash. Though technically the FBO stuff isn't tied to any particular card, the drivers may support it but not offer the extension for some cards. This will let it work find for some people and crash for others using the same driver version.
Basically, ATI drivers suck with regards to OpenGL, and they don't appear to care all that much about it. Nothing that we can really do about the problem though since, like most ATI related issues, it's a driver bug. You just have to use older drivers, or use -disable_fbo to turn off FBO support in the game.