This problem is under investigation (bug 25520). In the meantime, if you have experienced this problem, try doing the following:
Update - 3 August 2013 - The following steps should get your clippings back. Follow them first before trying the other approaches below:
- In Firefox, enter "about:config" in the address bar. In Thunderbird, invoke the preferences dialog (on Windows, Tools → Options; on Mac OS X, Thunderbird → Preferences; on Linux, Edit → Preferences), click Advanced, then click Config Editor.
- Search for the pref "extensions.aecreations.clippings.datasource.location"
- Change the value of that pref to your user home folder. For example, this would be C:\Users\username on Windows 7, C:\Documents and Settings\username on Windows XP, ~\username on Linux and Mac OS X.
- Exit and restart Firefox or Thunderbird
The original suggested steps for recovery are below. Try them if the above steps don't work:
- Open Clippings Manager, select Tools → Restore and choose the most recent date/time that appears in the menu.
- If that doesn't work, select Tools → Import, browse to the Clippings backup folder (e.g. for users on Windows 7 this would be C:\Users\username\.clipbak; on Linux and Mac OS X, it would be ~/username/.clipbak), and then choose the most recent backup file