Hi Dave
Had a similar prob with one of my pc's unsure if yours is the same but the stick of ram that was giving me greif was only single sided ram which didnt mix with my double sided ram but my pc refused to start if i had them in together .
hoped this helps if not hope someone else can cheers

 

Another possibility is simply that your board doesn't support 3 sticks. Check your user manual. Some only take 1, 2 or 4 sticks. 3 will lock your system up.

 

There are 3 stick slots on the motherboard, maybe it's only configured to support 2?

 

If you only have 3 slots, you can assume your motherboards supports 3 sticks, so that's not the problem.

Herbster's post above sounds like a high possibility. Did you look into that?

 

Try putting the largest capacity stik in Slot 1...refer to your MBoard manual to determine which slot is slot1.

patio.

 

The M/B supports only 128mb x 3 modules not 256mb each module

 

How do you figure each slot only supports 128? The capacity of the m/b is 1.5 gb.