You are probably on the right track in suspecting graphics card drivers. I don't use VL anymore but it is a great solid distro based on Slackware.
1. Changing the screen resolution and/ or color depth
2. See if you can disable 3d hardware acceleration in the VASM control center and see what happens
3. If these don't work, then try loading the VESA graphics driver at boot
hope this helps
Edited by Trio3b, 06 October 2009 - 11:08 PM.