I had a very annoying problem in Firefox that almost caused me to give it up and move to another browser. The biggest problem was that it was most apparent on the JavaRanch, and that just wasn't acceptable. I managed to find the fix after spending a long time searching for a solution with no success, so main main reason for writing this is the hope that it will help others that may be having the same issue.
Firstly a description of the behaviour I was seeing... While loading a page, Firefox would lock up and become completely unresponsive for a period of a few seconds. Not just the tab that was loading, mind you: it was the whole application. It would also cause the rest of the computer to be unstable, but I didn't really look into whether there were any memory or CPU issues, although it certainly felt like it. Opening multiple tabs at once felt like it would cause a disproportional wait, ie two tabs would take more than twice as long and worse for more tabs.
I was also seeing other strange Firefox behaviour, such as the occasional thread getting submitted twice which just added to my aggravation.
I tried removing all of my superfluous Firefox plugins, but stuck to the ones that I always use and also tried installing an older version of FF but nothing helped. I also tried some config settings but no luck there either.
The strangest thing that I noticed was that since I am in the process of transitioning from WinXP to Ubuntu (which the FF problem delayed) I noticed that this issue was also happening in my dual boot Ubuntu environment. Weird. I still couldn't believe I couldn't find anything on 'the net'.
Finally I found something pointing to issues in Adblock Plus, and although in the thread they stated it had nothing to do with them, I turned this off and *poof*, no more problems. I turned it off in Ubuntu and *poof*, fixed that too. Then I went to their site to file a bug report, and it was not user friendly and too much effort (probably another thing to thank spammers for) so I couldn't be bothered. Sad but true.