At the console or command line type "startx" and then copy and paste the output
to this thread. Maybe someone will be able to tell you whats wrong.

Sounds like an xserver issue. If you are in a hurry to get this working, and want to
try configuring x ( assuming the output from "startx" is something like "fatal server error" )
you could use "dpkg-reconfigure -plow xserver-xfree86" which will run a program to
configure x based on the specifications you input.