Hi,
You should make a good backup of anything on that drive in your Mac Pro.
For normal files, a backup via TM is fine.
For virtual machines TM is not reliable.
Copy other VMs by hand or use the utility Vimalin that I wrote and for which you can find a link in my signature.
Yes I know that error -36 is an error specific about files of which the file name start with "._"
It is only Finder that makes such files and you should not get an error on a disk slice as those files do not start with a dot underscore in their name.
So something worse is going on and IMO the disk your VM lives on is no longer to be trusted.
What happens if you try to copy the slice itself to an external disk? With the VM shut down of course.. do you get an error then?
Even if you cannot copy the whole VM to an external disk, try to copy as much files in the VM as possible.
There is a chance the VM can be repaired via some of the data recovery wizards (Andre or Ulli) that are also here at these forums.
--
Wil