'View Source' not working in IE6

[#1]

Hi guys
As the title suggests 'View Source' in IE6's right click menu and the View menu isn't working.
It won't show me anything in notepad at all. This is a clean system installed just 3 weeks ago. What is ironic is that I've also noticed this at work with IE7.
I've not installed any updates to break the system - just SP2.
Any ideas?

[#2]

Yeah I had this at work a lot, you need to clear out your temporary internet files and it will start working.

[#3]

Yup, done that and now it works! Yay!
I wonder why it goes wrong in the first place though?