I'm not sure there's much to worry about here -- there are no OS X viruses at present.

more worried about passing on a virus to the unfortunate PC owners, so would prefer to keep realtime scanner on as much as possible..

cheers

David

also wondering Dave, if this problem would still occur if not performing a full bootable backup?

Cheers

David

The PC owners have their own virus scanners, so I'm not sure this is something you need to worry about. In any case, no, Norton doesn't have this problem, and Intego didn't until their latest update. They're working on the problem.