I can reproduce this on multiple PCs on my network (but not all) but can't reproduce it outside the network.
One disturbing result of my testing is that I can't get IE to fault, only FF (tried v2 & v3)!
I've tried different DNS servers with zero difference in results. I have also tried disabling all my FF addons as well as starting a brand new profile, also with no differences.
Another odd thing is that (on an affected PC) if for instance I navigate to another page in IE (after a 2 minute wait), then try the same in FF immediately, it works quickly first time every time.
It's almost like there's some timeout somewhere which 'looses' the cached copy of the website's DNS entry or something strange and then when it is 'refreshed' by another process FF starts working properly again.
Anyone have any brilliant suggestions??
1 Open a new tab, and enter: 'about:config'
2 Click "I'll be careful, I promise!"
3 Search for the value: 'network.http.keep-alive'
4 Change this value to 'False'
5 Restart FireFox
Solution found here.
This actually appears to be an issue on the web SERVER side in conjunction with FF (see this page for the technical details - it's under the section 'Firefox Slow Page Load - Solved')