Frames in Internet Explorer disappearing

[Cavalier90]

I run a website that uses frames on all but the index page. Viewing at home on IE 6 and Firefox, the pages display in the frames correctly, moving from framed page to framed page with no loss of the frames. This used to be the case on my works computer as well. Now, moving onto the first framed page works OK but the frames are lost when navigating to another framed page. The works computer runs Win XP professional with IE6 SP1. A colleagues computer with the same spec displays the frames correctly, as did mine up until a few days ago.

I am not aware of doing anything to the settings to alter this, and cannot see anything in the settings to correct it.

Any clues? The website is http://myweb.tiscali.co.uk/mvtsc if this helps.