Unexpected error when copying files between guest and host using shared folders

Hello,

I'm using the Shared Folders feature to copy files back and forth between the guest virtual machine and the host machine.  This was working fine using Workstation 7 but since I've upgraded to Workstation 8 I keep intermittently getting the following error when trying to copy file:

   An unexpected error is keeping you from copying the file.  If you continue to receive this error, you can use the error code to search for help with this problem.  Error 0x800703E3: The I/O operation has been aborted because of either a thread exit or an application request.

Any ideas what might be wrong?

Thanks,

Greg