File copy between VM and host fails (almost) consistently

Emboldened by the quick resolution of my first problem, here I go again.

Same Win 7 VM as in my previous post, running on Workstation 9.0.1. Host is windows 8 x64

If I copy a bunch of folders from the VM to the host (drag and drop), copy fails, not all the time, but almost:

Cannot open local file for write

Cancelling the file copy operation

Sometimes the copy will work just fine. It seems to get worse with handling larger amouns of data.

Thanks,

Luca