On-access scanner disables Safari on-screen links

I've found that the Sophos AV (Mac) on-access scanner disables Safari on-screen links, e.g in a Google search.  It's a obvious as if when turned on no matter how much I try to click on a link - it will not tae me anywhere and locks up any link on that page - and when turned off it works fine?

Any thoughts?

(Safari 5.0.3)