My Google Toolbar (on Mac FireFox) went AWOL overnight – the bar was there at the top of the browser window but completely blank, no buttons. I tried the usual right click on the bar and Google Toolbar was ticked. I went to Google and downloaded and installed the Toolbar again, still nothing.
Then tried clicking Tools > Add Ons > Google Toolbar > Preferences and the Preference window was slightly bizarre with a number of buttons duplicated:
A quick Google Search found this page, and this piece of advice:
I removed everything in ~/Library/Application Support/Firefox/Profiles/<profile dir>/GoogleToolbarData
I followed the instructions, restarted Firefox and my Google Toolbar reappeared.