Well, the OP says he/she is using a "PC", so I'd assume they're using Intel x86 hardware with a standard SVGA monitor already attached (timresh, please could you clarify this - what hardware architecture are you using, i.e. is it SPARC or Intel?).

Try launching kdmconfig (from the command line after logging in) and going through that again as root.

If that still isn't working, you may consider installing XFree86 (good luck! ) so, try taking a look at this first
http://www.sun.drydog.com/faq/8.html

Cheers
ZB