I had a prefectly good new HP Z420 running MC 6.5.2 just fine on my bench waiting to get placed in a suite. When I installed P2 Drivers for our P2 viewer and reader device, MC was experiencing the dreded "Initializing Avid Media Access Volume Manager Freeze".
Once I uninstalled the 221 P2 driver, MC opened up just fine. I tried 2 more times with the same results. I then installed P2 Driver win64 v216 and MC opened up as normal. So it would seem there might be something in that v221 P2 Driver to watch out for. I only dicovered this by searching the net and found someone in the Symphony forum here had the same problem and by uninstalling the drivers, he was able to get past this same freeze. I don't know if that person was using P2 driver v221, but by reverting back to v216, it seems to have fixed it for me. I am now installing MC 6.5.3 and might try that newer 221 driver again to see if there is a difference.
YMMV
Good Luck
Grant