When a client is accessing their webmail using Usermin the following error appears. This does not happen on all logins as far as I have been able to determine.
Usermin 1.460 Webmin 1.530
HTTP/1.0 500 Perl execution failed Server: MiniServ/0.01 Date: Tue, 4 Jan 2011 10:50:18 GMT Content-type: text/html Connection: close
Error - Perl execution failed
sdbm store returned -1, errno 22, key "<firstname.lastname@example.org>" at ./mailbox-lib.pl line 1437, line 123.