[TYPO3] Problem with userrights

[Maurice Geurtzen]

Hello,

I have a problem with userrights on a site. Whenever a user tries to edit
an element he/she gets the following errormessage:

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Sorry, you didn't have proper permissions to perform this change.
Reason: ERROR: authMode "explicitDeny" failed for field "CType" with value 
"textpic" evaluated
-----

The problem appeared apperently spontaneously. With admin-rights everything 
works fine.
Can anyone help me?

Regards,
Maurice