[horde] Error when redirecting message

[Volker Then]

Hi there,

with the newest IMP (5.0.16) redirecting of messages is no longer  
possible. I'm getting the following error message in the logfile:

2011-12-20T13:18:31+01:00 WARN: HORDE [imp] PHP ERROR: array_flip():  
Can only flip STRING and INTEGER values! [pid 18939 on line 60 of  
"/usr/share/php/Horde/Imap/Client/Utils.php"]

Any idea?

Regards,

Volker