Also -- could it be the RAM -SLOT- that has gone bad, and not the DIMM?
To find this out, I think you'd have to do this:
1. Label the DIMMs ("1" and "2")
2. Begin with DIMM #1. Put it into the top slot. Leave the other slot EMPTY.
3. Run like this 2 days -- how does it do?
4. If good, put it into the bottom slot and run for 2 more days.
5. Did DIMM #1 work in both slots?
Then, repeat this entire process with DIMM #2.
If a slot is bad (not the DIMM), you could buy a new DIMM, and have the same problems again!