When I open the Organizer and click on e.g. "Views" a menu appears. Then when I move my mouse back to the toolbar and hover over "Import and Backup" this button gets the hover state but the menu of the previous button stays on the screen until I click. I think the menu should at least disappear as soon as I hover over another menu button and maybe even expand automatically like folders on the bookmarks toolbar.

dupe of Bug 397111 ?

Indeed.

Bug 451915 - move Firefox/Places bugs to Firefox/Bookmarks and History. Remove all bugspam from this move by filtering for the string "places-to-b-and-h". In Thunderbird 3.0b, you do that as follows: Tools | Message Filters Make sure the correct account is selected. Click "New" Conditions: Body contains places-to-b-and-h Change the action to "Delete Message". Select "Manually Run" from the dropdown at the top. Click OK. Select the filter in the list, make sure "Inbox" is selected at the bottom, and click "Run Now". This should delete all the bugspam. You can then delete the filter. Gerv