58 is getting sorta high imo. I would shoot for sub-50 on a dual-core OC (I have an X2 though).
I'd consider 1.43v low for voltage. My plan was to see what clocks I could get out of 1.5v through a C2D, but I planned on using water. There are plenty of people pushing 1.5v through a C2D on air though, but not necessarily with the Zalman 9500.
If you're failing Orthos, either increase the voltage or lower the clockspeed. Your BSODs are probably caused by CPU issues. That's why we use stress programs like Orthos/Prime95/etc; they show us potential weaknesses. If you fail Orthos, then that's probably an indication that your CPU is the issue.