Extensions for Firefox, such as the Google Toolbar, include a list of compatible Firefox versions. Currently, the Google Toolbar only goes up to Firefox 4. However, people have tested and it actually works on Firefox 5, so there are two workarounds:

(1) Edit a file to revise the range of compatible versions

(2) Install an add-on that lets you ignore the range of compatible versions

This thread has info on both approaches: google toolbar does not work with firefox 5.0. why not! | Firefox Support Forum | Firefox Help.

Any luck?

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Here's the process to roll back to 3.6.18:

First, I recommend backing up your Firefox settings in case something goes wrong. See Backing up your information. (You can copy your entire Firefox profile folder somewhere outside of the Mozilla folder.)

Next, download and save Firefox 3.6 to your desktop for future installation. http://www.mozilla.com/firefox/all-older

Close Firefox 5.

You could install Firefox 3.6 over it (many have reported success) or you could uninstall Firefox first. If you uninstall, do not remove your personal data and settings, just the program.

Unless you have installed an incompatible add-on, Firefox 3.6 should pick up where you left off. If there are serious issues, please post back with details.

Thanks, rolled back successfully!

Please click the Solved It button next to the answer that answered or solved your Firefox support issue, it appears when you are logged in, so this thread gets marked as Solved to help other users who may have this same problem.

You guys did some serious damage to my browsing experience since ver 3... I've been a avid firefox user since the beginning but now I'm leaving firefox and switching to chrome... seriously, why did you guys screw up such a wonderful browser! I know I don't pay money for it (though I have donated in the past) and I'm glad I did not pay for this because I would be demanding my money back for sure!!! So, I guess since I don't pay, I have no right to complain but I just wanted you guys to know how utterly disappointed I am as I move toward a lesser browser... I say lesser because it does not provide the rich environment I was spoiled with in FF 3 but... it is now a better browser than FF4 -5 since 4 -5 are so heavy laden with junk and ads and redirects and lack of functionality... I'm very, very disappointed.

Firefox 4.0 and later does NOT come with junk and ads and redirects such if you got Firefox from Mozilla and not some random unofficial site.

NO FF 5 sucks! I do not have Google tool Bar I got rid of most of my add on except for Ad Block and it kept freezing, threading, hanging! Now my 3.6 is not working as well as it was before. I hate IE and IE is working better than FF or Chrome... guys please don't make me use IE!

Version 6 sucks too - much worse than 5!!