After a few hours of playing, my framerate will start dipping suddenly and noticeably. Within 10 minutes of that, the client will close with the following error in a dialog box:
Fatal Error: There is not enough available video memory. Please choose lower resolution settings, or close other graphics and applications.
Technical Details: D3DERR_OUTOFVIDEOMEMORY while creating 2D render target texture size 1440 x 900(D3DMFT_NVIDIA_INTZ_DEPTH_TEXTURE_FCC)
Restarting the application produces the same error while loading to the character select screen. I'm running a 4870 x2 single-board configuration. Using ATI catalyst drivers 9.11 (9.12 prevents this machine from booting). This error occurs both with crossfire and without. It occurs both in windowed mode and fullscreen. The conditions leading to the crash only seem to occur after several hours of play.
I have dozens of highly intensive games on the machine which all run beautifully and do not complain about a lack of video memory. After this crash I can load, for example, Mass Effect 2 and play just fine. The error doesn't affect the loading or stability of other applications at all.
Resolution involves rebooting the machine of simply waiting between 10-30 minutes and launching the application again, at which point it will load and run fine without the error occuring.