Same problem here with two Win2k8 R2 x64 servers and also TSM for VE.
TSM for VE is taking a snapshot with the memory option 0 and the quiesce option 1.
I bet you can't take a manual snapshot of that vm with unchecking the memory option and checking the quiesce option.
I couldn't find a solution for that.
Any idea why the snapshot works when memory option in checked and quiesce is checked too, but it doesn't work with memory 0 and quiesce 1?