Vista - Computer back-ups & Live Snyc

I use Live Sync between two computers behind a wireless router firewall. I
do not sync any data beyond this firewall between the computers. When
backing up the data either of these computers, it stops when it reaches the
folder associated with the data I linked with Live Sync, indicating the
folder cannot be backup'd because the folder is in use. How do I get around
this problem?

My backups are done manually at the moment, copying files from one HD to
another. I would like to automate this if I could, but I need t resolve this
issue first. Thanks for your assistance.

Doug