[horde] Blank page after login

[Philipp Fäustlin]

Hello.

One of my users gets a blank page after login to webmail on every system 
we tried.

I have tried it even on a test system with a empty database and horde in 
the newest version.

The login method is imap auth and the horde.log says "Login successful".

In httpd/error.log I found an
PHP Fatal error:  Method Horde_Imap_Client_Mailbox::__toString() must 
not throw an exception in /usr/share/pear/Horde/Imap/Client/Socket.php 
on line 1284, referer: http://WEBMAIL/login.php

I think this error is the reason for blank page, but I don't know what I 
can do against it.

Thanks in advance.

Philipp Fäustlin