Google needs to update the Google Toolbar program for Firefox 5.0.

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

thanks for the answer, a least i now know why it doesn't work

My wife's machine lost the toolbar when she updated to FF 5. Why should I upgrade my machine. until his issue is resolved? It's not very good for you to upgrade when a very useful tool is not compatible. You should have assured Google was appropriately prepared for this. Are you going to force me to switch over to Chrome? I know you're not issuing regular updates any more so is this issue going to surface each time you issue an upgrade?