After the lastest round of updates were installed from Microsoft, I foolishly forgot to uncheck the "Upgrade to I.E 7" box and hence after a reboot, a fresh new version of Internet Explorer was waiting for me. On face value this appeared ok until I tried to access Mercury Test Director.
According to the error message, only I.E 6 was supported.
A quick search on google and I happened upon this website: http://tredosoft.com/Multiple_IE
and downloaded the installer which contained multiple version of I.E from 3.0 to 6.0 that run in standalone.
Not only has this fixed my problem of accessing applicaitons, it also allows me to test my applications against earlier versions of I.E.
Very useful indeed