super pi is a cpu mainly test so it miust be somthing to do with the cpu, have you tried any other stress test i think the intel one is fairly harsh?
you on vista?
silly fix if its the problem i think it is, when its asks ok to run the test, move the ok box to a corner of the screen before you click ok.
1 hour Orthos test was stable too.
have you tried my fix?
Incidentally, how long was the memory wall tested for?
Try OCCT some people don't like it but I've found it will often trip inside 20 minutes on faults that otherwise took 8 hours in multi prime/orthos to show up.
As super Pi (atleast 1-2M tests) will usually run fine even on systems that aren't 1 minute prime stable I'd look elsewhere before blaming it on the CPU.