What version of Knoppix and X do you have BrittBS? I'm having a similar problem with an ECS Desknote A901 which has the sis630 chip. I am using Knoppix 3.2-2003-06-06-EN installed on the my hard drive (but booting from the CD gives the same problem) with XFree86 4.3. Didn't have this problem with RedHat (but there were other problems with that and XFree86 4.2.0). What happens if you do startx with the -depth or -bpp options?