I am having the same problem on my IBM NetVista desktop with integrated Intel 845G graphics.
By default, the driver is "vesa", I tried changing this to "intel" and "i810" and neither of those worked, I got just a black screen. Even under "vesa" the only resolution it would display is 640x480x16. Changing the DefaultDepth to anything else, I got just a black screen.
This is with Slackware 12.1.