I lost my adresses when new release downloaded--lost all my contacts--how to get back?

Try this: - click help>troubleshootinginformation - scroll down to 'Profiles' in left column and click 'about:profiles' - the next pane should list all profiles available. Click the 'open' button to view profile contents. The addressbook consists of two files: abook.sqlite and history.sqlite - if you look in the inactive profile and the size s bigger than the one in the default profile, then you have discovered your addressbook. Note the file location. - now, return to thunderbird and click tools>import>import from a file and follow the menus for addressbook until the select of file type appears. Click the sqlite option and then select the abook.sqlite file from where you located it. Repeat the steps for the history.sqlite file