Startup screen: bizarre patterns & flickers

Question

I'm on my work's G5 flat screen iMac, X.3.9, 1.8ghs with 768 mb ddr sdram...
Over the past week, on startup, it chimes as normal and several kinds of things happen.
1. a grey screen with a load of code, then a black square basically telling me to shut down and restart.
2. a grey screen with the apple logo, but a scratchy flickery screen, like on old black and white TV set.
3. a plain colour, usually green or orange with 1cm small dark horizontal dashes across the whole screen.
The past couple of days it does a combination of the above, and it takes about 3 shut downs/restarts to get to a normal start up. During the day there are no problems at all until the next morning when I start up.
Anyone recommend anything? Nothing too techy-speak, just simple instructions will do. All I've tried is PRAM, but it made no difference.
Thank you
Loo

Answer 1

Hmm. I'd say so. If you take all the memory out and clean the contacts on the motherboard (Q-tip works best) or just blow some air through them and then reseat the memory, that could help. System test is pretty darn reliable, but I'd just give that a shot before you end up buying a new stick of memory.
HTH,
~FifthWheel