ok, sorry for all that but it was my fault.
i set hasMain to 0 in the database, so the permissionbuttons for the main-poll-moduls got lost (whyever). i just checked if the groups got all buttons checked (was the case) so i didn't see that the permissions for that module were missing.

now i set hasMain to 1 and the checkboxes are there again. the permissions were missing.

sorry again.