Sometimes thunderbird creates a new profile on updates. So, my guess is that it is there somewhere. Try this: - click help>troubleshootinginformation - scroll to 'profiles' and click 'about:profiles' - if more that one profile is listed, your addressbook may be there. - click 'open folder' on the suspect profile - look for a file named 'abook.sqlite' and see if it appears to have been recently updated. Note its location on disk - in thunderbird, click tools>import>import from a file - follow the addressbook links to the screen with 'sqlite' as an option. click there and then select the 'abook.sqlite file you found - repeat the step to import the related 'history.sqlite' file