Error -36 nightmare

Hi All,
If someone could help me, they will prevent rapid onset hairloss.

I have a MacBook Pro (with Lion) networked to a Windows 7 machine. I have a folder on my desktop with about 50GB of stuff that I want to transfer to the Windows computer. Simple?

Network is fine, can even run a remote desktop, etc etc.
Everytime I go to transfer a file I get Error -36. "The Finder cannot complete the operation because some of the data in smb://........ could not be read or written. (Error code -36)." Or something similar.

Any suggestions? I'm stuck.