virtualbox.org

I'm using a Mac host, 10.6.8, with a Windows XP guest. I have an issue with the video reverting to 640 x 480, then not being able to be changed to the normal 1200x800. I have all of the resolutions to select, but if I choose anything higher than 1024x768, the VM reverts back to 640x480, and 4 colors. What's wrong? Is it the XP install or a corrupted video driver? I am usine the Guest Additions.

How much display memory did you give the guest? In fact, post a VM log - I'm sure you've been around here long enough to know you need to do that.