Attaching a monitor to my laptop problem

[ski]

I'm running Windows Vista and have an ATI X 1400 Graphics card and a brand new pimped out lappy.

The monitor works well with my desktop in a dual monitor setup but not with my lappy. What gives? I just get a blank screen with a "Check signal cable" message. I've tried both analog and digital cables and neither works. The monitor is a Samsung syncmaster 204B.

Any ideas?

Thanks,
Ski