Question about purpleish screen

[John Marr]

I just installed the latest version of videolan from the web site from the deb package. 

Incidently, the video resoultion and stability is MUCH better then the MS Windows windvd player that came with my laptop. 

While my laptop is plugged into my 19" monitor, the resolution and playback of dvds is impeckable. Yesterday, however, I unplugged my latop from my 19" MONITOR and tried to watch a dvd from the 15" laptop screen. While the sound works fine, I can only see a purpleish screen. No picture. When I plug the 19" monitor, everything works fine. 

Am I doing something wrong, or is there an option that I can set to fix this.

Dell Inspiron 8000 1 ghz.
256 mgs RAMM
NVIDIA GFeForce2 Go Video card
Debian unstable

Thanks in advance, I hope you can help me