Why is my internet really slow and keeps freezing ever since I updated to Firefox 3.6.23 ?

I updated to Firefox 3.6.23 and now my internet/Firefox is acting really strangely. It is suddenly running really slow now and also likes to freeze up sometimes ("not responding"). And sometimes when I click somewhere, nothing happens. It just seems really unstable and once again, I wish I hadn't updated to the new version. It seems that whenever I update my Firefox, I end up regretting it. I don't have the time, computer knowledge or patience to have to always try to fix the problems that the updates always seem to create. And because I work from my home computer and from the internet, these updates really negatively affect my work. :( As soon as I get the problems fixed from previous versions of Firefox, they release a new update and I'm back to "square one." Ughhhh!