Sorry guys for not responding earlier......
Tnx for putting me on the right track; I ended up with timing setting 7/7/7/30, VRam 1.64, multipl. 10X
Everything seems stable now at 1333 MHz (memory)
Prime95 gives me the occasional error report but I think that has to do with one of the old PCI cards I use.
Without the PCI cards it's rocksolid esp. with W7 64bit (wow, really quick machine with that op.sys.!!)
All other stability tests report a stable system (with PCI cards inserted)
I'm almost starting to think Prime95 isn't the best testing software for everyone? (but what do I know :-)
Cheers, I'll drink one in your health! ;-)