Funnily enough Steve, I suspect it *is* to do with settings on the local browser being changed - especially if you haven't had a problem before. The coinmill Mod calls a javascript which 99.9% of browsers handle perfectly well - but sometimes, just sometimes, it falls over when the browser doesn't handle the call correctly.
I wrote this particular mod some time ago and it has been running on this, and two other busy forums, for over a year now; this is the first time there has been an issue that anyone has highlighted. I'll insert a detection script that will cancel the javasript before the browser falls over and send to you to add shortly.
JF