Google hasn't updated the Google Toolbar extension for Firefox 5.0 yet.

The GTB 7.1.20110512W version works in Firefox 5.0 by using the Compatibility Reporter extension, I tried it myself due to the large number of postings about the GTB this morning.
https://addons.mozilla.org/en-US/firefox/addon/add-on-compatibility-reporter/

On MAC the toolbar isn't working and I can't find the MAC version of the GTB mentioned above. Second time I've installed a new Firefox version and had to revert to previous working model. Currently on 3.6.17 which works perfectly. Version 4 killed all my bookmarks, version 5 killed the Google toolbar. Not bothering to upgrade anymore until I know product is tried and tested. Note to Mozilla: there is no point in rushing out software which causes problems. If you want me to go over to Chrome you're going the right way about it.

For Google toolbar there is a quickfix for firefox 5.o See: A. Jooms post here: https://support.mozilla.com/en-US/questions/837142?s=Google+Toolbar+for+Firefox+5.0&as=s

I suggest everyone who likes their Google toolbar uses IE9 or Chrome until Firefox gets an update. It isn't secure using Firefox 5 without upgrading it - they should have liaised with Google before releasing 5.

The solution is to install the Add-on Compatibility Reporter. It will force Google Toolbar to work. You can find detailed instructions here: Re-enable add-ons that were disabled when updating Firefox

memsahib, the Google toolbar is made and maintained by Google, not Mozilla. If Mozilla were to have Firefox 5.0 just sit around until Google finally updated their toolbar then Firefox 5.0 may never get released anytime soon.

Google is already a few weeks late and had Betas 1-4, 6, 7 of 5.0 that they could have worked and tested with before 5.0 release.

Am I the only one but is GOOGLE been an ass, not supporting Firefox 5 or higher Topical of Google.

A month after the Firefox 5.0 release Google finally came out and officially said they are no longer supporting their Google toolbar extension for Firefox anymore.

http://googletoolbarhelp.blogspot.com/2011/07/update-on-google-toolbar-for-firefox.html

http://www.google.com/support/toolbar/bin/answer.py?answer=1342452&topic=15356
https://support.mozilla.com/en-US/kb/google-toolbar-not-compatible-firefox