The same thing happened with my Compaq Presario V6000

It could be memory but I solved the problem by changing the refresh rate to 60 Hz

On the first screen you get at the bottom you will see
BOOT:_
type in knoppix xvrefresh=60

Take a look at this link if you need more info

ftp://ftp.mirrorservice.org/sites/ft...t_details.html