Extended Monitor Problem

[kenpattx]

I was working thur nite while in the middle of a song the lcd monitor goes black..I checked the cables, the ac cord, ok..I spent quite a while on display settings...settings are right I think..during all this I left the songs playing in auto mode.. the extended monitor would come back on for maybe a minute then for no reason go black...this laptop is a Dell Inspiron 6400, about 2 years old, it has done three shows a week for the past 2 years its been a great laptop...specs are'nt great....1.66ghz...980mhz....504mb ram...
I had an old laptop in the van its one of the first sold by mtu, it still works except its wore out...I hooked it up and finished the nite..monitor and cables are fine....the dell is fine in every respect except for the.. extended monitor..
any ideas or help would be appricated...thanks Ken