Error Code 0?

[gtrcoop]

I have the following:

 

- MacBook Pro

- Buffalo 750GB External Hard Drive (Firewire)

- WD 1TB External Hard Drive

 

I'm trying to transfer files from my WD drive to my Buffalo drive and receiving the "The operation can't be completed because an unexpected error occurred (error code 0)" message when moving the files.  

 

This is odd because I've moved the same files in the past to the Buffalo drive with no errors.  In addition, some files DO transfer with no problem but I find that odd in that they are on the same WD 1TB drive.

 

Any ideas?

 

Thanks in advance!