No signal output to TV via VGA

Hi all,

I have a problem as follows:
I connect my HP nx6325 to my TV set and press fn+F4, no signal output to TV. Did someone know how to fix this problem. My OS is OpenSuse Linux 11.1. Thanks!

hfu

Some more information about this problem: when I connect to TV and switch to TV display, no signal to TV. If I reboot the computer (the cable is still connected), my computer can not start up correctly. The TV is black and the LCD of my computer is also black.