grey display, macbook 2008 aluminium

I left my macbook powerred up and nextmorning it didnt startup any more.

I only have a grey screen.

I have tried several reset options nothing is helping.

http://support.apple.com/kb/TS2570

even if I try to boot from USB drive its not starting.

but it is palying the startup sound.

when you wait a moment, you can see that the screen is a bit changing, but its still grey.

from that point, if i press on brightnes buttons its getting dark or more light.

thus i think its something withe my videocard.

its a13" aluminium macbook from 2008.

please can you help me??

thanks