https://bugs.freedesktop.org/show_bug.cgi?id=35051
--- Comment #11 from Brian Paterni bpaterni@gmail.com 2011-05-16 09:15:04 PDT --- Thanks for the confirmation there.
I did end up running Steam/CS: Source through zach rusin's apitrace tool, getting the following trace:
http://uploading.com/files/1213aed2/css.glapi.trace/
the erroneous call seems to be
235567 glDrawBuffer(mode = GL_BACK) 235567: warning: glGetError(glDrawBuffer) = GL_INVALID_OPERATION Mesa: User error: GL_INVALID_OPERATION in glDrawBuffer(buffer=0x405)
Hopefully this helps greatly in the debugging process. :)