if the ram works in the other system and doesn't in the current one, your guess can be pretty strong that there is something wrong with the RAM slots or the logic board.
I think that you need to take the first step in resetting everything, the logic board, remove the battery, remove the ram and put it back, etc. If all of this doesn't work, then you may have bad logic board in the system.
"Fix it 'til it Breaks."
Jacob - EiC & Director of Technology Mac Pro Quad 2.66 - 4GB RAM 160 GB SATA RAID 1 - 650 GB Storage Quad 19" Widescreen LCDs Accessorized to the Hilt
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