Failing Orthos in Blend mode means that your pushing your memory or FSB too far at your current settings.
Have you tried to lowering your FSB, and bumping up the mulitplier to 9? So you can still have your CPU running at 3.4. This might take some stress off your FSB and solve your problem.
If I recall isn't the stock setting for that memory 5-5-5-15 @ 2.2v? If it is, try looseing your timings and run them at 2.2v.
I would try one, then the other. And if that doesnt improve anything try both.
If your still having problems, maybe you could try to back off your OC slightly.