AHHH Powermac G4 wont startup PLease HELP???

Hey guys bit of a panic:

I was doing my normal stuff(browsing these forums and ebay) on my Powermac G4 when suddenly i got one of those evil OSX Tiger please restart screens popup in the middle of my screen telling me to restart my computer by hitting the reste button or holding the power button for 6 seconds......I proceeded to do this and myu powermac now wont boot properly!!!

So now my powermac switches on but doesnt show anything on the screen my monitor remains black. I have tried re-seating the graphicscard and RAM but neither have done the trick.

I would be very grateful for some help and if anyone would know what the cause of a problem like this could be i would like to know.

Thanks in advance,

SHadow

Thanks given all these a try but still no luck think i have to get hold ofa new PRAM battery, but any iother suggestions are welcome,

Thanks

Solved the problem by replacing the battery, it was 6yrs old after all, well the Yikes will do for now until i get my mac mini,

Thanks,
shadow