It's a wireless router Barra.  I'm positive that it's caused by aggressive scrolling because that's the only time it happens.  Since I've uninstalled the mouse software all seems to be  well, so fingers crossed.

I'm positive that it's caused by aggressive scrolling

Well stop being so aggressive  

Clive, can't you configure the mouse to scroll slower?

Well, after all this, it'll be bloody funny (but not unusual) if something so simple cures the problem!!  

The old mouse has been installed for over 24 hours now and not a single crash.      

To be honest with you I was very nervous about the way it used to glow eerily in my hand.  It seemed to be giving off some strange unidentified radiation.      

I've established that the fault isn't specific to the optical mouse.  I've also had a few freeze-ups with my old mouse too.  I've run Norton's Windows Doctor and it can't find any faults at all.  It still only happens when I use the scroll wheel.

That's an interesting point Simon.

Clive you might want to go here and download & install the latest Detonator drivers.

You never know, it may just work   (at least it'll be one more thing off the list).