For a long time, I was encountering problems with Firefox on Windows. Especially on Ajax-sites, but also on various other sites, Firefox all of a sudden seemed to load and load and load forever – without even doing anything… The only possibility was then to shut down Firefox and kill the task in the Taskmanager.
After having read loads of stuff, I suspected that the problem was caused by a combination of my Virus scanner and my firewall.
The Virus scanner I use is AVG – as previously listed. I found a website that helped on uninstalling the problematic AVG linkscanner (it is listed as a problematic extension in Mozilla’s Knowledge Base), I did so.
Also, I got rid of the Ashampo firewall in use and switched to Comodo Firewall.
Now, after 1 or 2 months of surfing and browsing, I never encountered the problems any more – the only problem persisting is that Firefox sometimes does not end the task correctly, but this is only AFTER I exit the program – so I sometimes still need to end the task, but my browsing experience is unaffected. Phew… 
