ERROR: hook /usr/share/apport/package-hooks//source_thunderbird.py crashed

I don't see how this could happen. Could you please send me the prefs.js file from your profile folder (and the user.js file if there is on)? Also, what addons do you have installed?

Here is what I get from "Troubleshooting Information" (it says 14.0a2 but I hadn't upgraded yet at the time):

  Application Basics

    Name: Thunderbird
    Version: 14.0a2
    User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120502 Thunderbird/14.0a2
    Profile Directory: Open Directory

              (Local drive)
    Application Build ID: 20120502102331
    Enabled Plugins: about:plugins
    Build Configuration: about:buildconfig
    Crash Reports: about:crashes
    Memory Use: about:memory

  Extensions
    Add-on Compatibility Reporter, 1.1, true, <email address hidden>
    Dictionnaire français «Classique &amp; Réforme 1990», 4.3, true, <email address hidden>
    Dictionnaire français «Moderne», 4.3, true, <email address hidden>
    Display Contact Photo, 1.2.5, true, <email address hidden>
    EDS Contact Integration, 0.3.9, true, <email address hidden>
    Global Menu Bar integration, 3.2.4pre, true, <email address hidden>
    Lightning, 1.6a2, true, {e2fda1a4-762b-4020-b5ad-a41df1933103}
    Mail Redirect, 0.7.6.10, true, {CC3C233D-6668-41bc-AAEB-F3A1D1D594F5}
    Messaging Menu and Unity Launcher integration, 0.9.3, true, <email address hidden>
    Provider for Google Calendar, 0.15pre, true, {a62ef8ec-5fdc-40c2-873c-223b8a6925cc}
    Test Pilot for Thunderbird, 1.3.9, true, <email address hidden>
    Thunderbird Conversations, 2.3.2, true, <email address hidden>
    Libnotify Popups, 0.1.4, false, <email address hidden>
    MoreFunctionsForAddressBook, 0.6.7.2, false, {3e17310d-82e8-4a43-bd2f-7c3055bfe589}
    Mozilla Labs: Contacts, 0.4.2, false, <email address hidden>
    ThunderBrowse, 3.8, false, <email address hidden>

  Important Modified Preferences

    Name: Value

      accessibility.typeaheadfind.flashBar: 0
      browser.cache.disk.capacity: 1048576
      browser.cache.disk.smart_size_cached_value: 583680
      browser.cache.disk.smart_size.first_run: false
      extensions.lastAppVersion: 14.0a2
      gfx.blacklist.suggested-driver-version: <Anything with EXT_texture_from_pixmap support>
      mail.openMessageBehavior.version: 1
      network.cookie.prefsMigrated: true
      places.database.lastMaintenance: 1335955948
      places.history.expiration.transient_current_max_pages: 92575
      places.history.expiration.transient_optimal_database_size: 148119224
      plugin.soname.list:
      security.disable_button.openCertManager: false

Thanks, I've fixed this now, along with some other edge cases too