Module cannot be activated properly when using table prefixes

When I activated the Module I got an error message:

user warning: Table 'usr_web55_1.tasks' doesn't exist query: INSERT INTO d1_tasks_advanced (nid, taskcategory, tasktype) SELECT t.nid, 'unknown', IF(t.nid IN (SELECT parent FROM prefix is missing here tasks), 'project', 'action') FROM d1_tasks t LEFT JOIN d1_tasks_advanced a ON t.nid = a.nid WHERE ISNULL(a.nid) in <Drupal installation path>/includes/database.mysql.inc on line 172.

I installed Drupal with a table prefix "d1_", the database name is "usr_web55_1". It simply seems to me like one table prefix for the "tasks" table is forgotten.