Wow, lots of new Messages since I last checked. Thx for spending so much time on my Problem. I will try to Experiment with all those hints, right now I'll answer a few things that come to my mind.
I'm still uncertain about this moref stuff. For PrepareAccess, you said, I should call it with "moref=vm-{number}" if I use vcenter and for esxi I should not call that method at all. Now, for the snapshot, I get something like this "moref=vm-5-snapshot-56" from vcenter and something like this "moref=5-snapshot-56" for esxi. Should I add a "vm-" there in esxi case ot remove in the other?
Meanwhile 3 vms have this issue for me: A MS DOS 6.22 VM and a Win7 32bit.