OS: Windows XP 5.1 (Build: 2600)
CPU: GenuineIntel Unknown processor @ 2400 MHz with 511MB RAM
Video: ATI MOBILITY RADEON 9000 (Omega 2.5.58) (6458)

Assertion failed: RenDev [File:.\WinViewport.cpp] [Line: 471]

History: UWindowsViewport::OpenWindow <- UGameEngine::Init <- InitEngine

I've been playing fine for awhile now... what should I do?