However, my first guess would be the ATI graphics card. Do a test by turning off Hardware Acceleration (Window>Preferences>OpenGL). Its a hit and miss affair to find a graphics driver version that works, but you could try it. At the time, Google is discouraging people from using ATI or Intel graphics solutions on their Hardware requirements page http://sketchup.google.com/support/bin/answer.py?answer=36208&cbid=1tm6vzbb1xjzj&src=cb&lev=index
Anssi