I just reverted to back to Octa-Capture drivers 1.5.1 on win 7, 64-bit
I had numerous crashes (too many!) with X3b and X3c in the last 2 weeks and I can't believe all of them are X3 bugs - especially the repeated problem that Sonar would crash when changing ASIO buffer size (never had that before) and after reverting to OC v1.5.1 it seems gone again (fingers crossed!)
(Note that I use vs-700 and octa-capture in vs exp mode.)