Unsubscription problem

[Thomas Bretgeld]

Hi,

trying to unsubscribe from the mailing list, I get this error:

Bug in Mailman version 2.1.11

We're sorry, we hit a bug!

Please inform the webmaster for this site of this problem. Printing of 
traceback and other system information has been explicitly inhibited, 
but the webmaster can find this information in the Mailman error logs.


Can someone please fix this?

Kind regards,
Thomas Bretgeld