"General error: 2006 MySQL server has gone away" when adding menu block

Hi,

Everytime I click on "add new menu block" I get the following error message:

Additional uncaught exception thrown while handling exception.
Original

PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: SELECT s.lid, t.translation, s.version FROM {locales_source} s LEFT JOIN {locales_target} t ON s.lid = t.lid AND t.language = :language WHERE s.source = :source AND s.context = :context AND s.textgroup = 'default'; Array ( [:language] => de [:source] => Configure how content input by users is filtered, including allowed HTML tags. Also allows enabling of module-provided filters. [:context] => ) in locale() (line 684 of /html/home/modules/locale/locale.module).

This problem appeared after I deleted the existing menu block for the secondary links of the main menu.
Reinstalling the menu block module has not had any effect.

Any suggestions?