While playing UT2004, the mouse seems to stop responding in the game, e.g. if I run around, I can't look using the mouse, but can strafe and jump using the keyboard. I've tried lowering the graphics, but it doesn't help.
I don't think it's that it's that the surface is too shiny (it's an optical mouse) as I've never had any trouble outside the game, and it only seems to be in UT2004.
I have a Celeron 2.6ghz machine with 512mb RAM and a 128mb ATi Radeon 9200SE PCI graphics card, and an optical USB mouse. It runs Windows Server 2003 SP1 with Direct X 9.0c.