PowerMac boot up problems

One of my clients has a PowerMac G5, dual processor system. It started getting to where when it was turned on, the screen wouldn't come up, and the fans would begin to rev up like a jet a take off.

I took it, and started trouble shooting. MOst of what I've found lead me to believe it is a RAM slot issue on the first matched pair slots.

I removed her current RAM, put in new RAM. I put in 4 x 1GB sticks, rebooted, and got the machine to come up.

I checked About this Mac and only showed 2 GB of RAM.

I did some trouble shooting, and found, by moving those four sticks to matched pairs 2 and 3, and putting my own 512 MB matched pairs in the first slots (a total of 5 GB) that it only showed 4 GB of RAM.

So, I believe that the first matched pair slots are damaged, or not making good contact.

I have found that after seating the RAM in slot 1, the machine will boot, but after a bit, it will Grey Screen on me, or on subsequent reboots will go back to not coming up completely.

Any help ona correct fix for this issue would be greatly appreciated.

Also, should I have to have the RAM in slot 1 positions for it to boot?

It's the dual core model that supports 8 GB RAM. I have tried using the SMU button as well. Actually didn't fix anything as far as the boot up. I will give that another go....but I'm pretty sure that the first position for the RAM may be disconnected from the board somehow.

RAM slots are 8 in total. 4 match pairs.

4 top, 4 bottom. Not sure that helps.

Brian