Horde vacation plugin not working

[ATS-User]

Hi,

I got a Plesk 9.3 Server and just installed the horde vacation plugin as described here.

For a short time (2 months) it worked perfectly. But now it´s not working anymore.

If I go to my webmail account and select the vacation option, i get only a blank site. I changed nothing on the server. So I don´t know why this happens.

This is from the apache error log.

[Tue Jan 08 16:32:50 2013] [error] [client 1.2.3.4] PHP Warning: DOMDocument::loadXML() [<a href='function.DOMDocument-loadXML'>function.DOMDocument
-loadXML</a>]: Start tag expected, '&lt;' not found in Entity, line: 1 in /usr/share/psa-horde/lib/Horde/DOM.php on line 126, referer: http://webmail.sfb-d.d
e/services/portal/sidebar.php
[Tue Jan 08 16:32:50 2013] [error] [client 1.2.3.4] PHP Notice: Trying to get property of non-object in /usr/share/psa-horde/lib/Horde/DOM.php on li
ne 376, referer: http://webmail.xy.com/services/portal/sidebar.php
[Tue Jan 08 16:32:50 2013] [error] [client 1.2.3.4] PHP Notice: Trying to get property of non-object in /usr/share/psa-horde/lib/Horde/DOM.php on li
ne 379, referer: http://webmail.xy.com/services/portal/sidebar.php
[Tue Jan 08 16:32:50 2013] [error] [client 1.2.3.4] PHP Fatal error: Call to a member function hasChildNodes() on a non-object in /usr/share/psa-hor
de/lib/Horde/DOM.php on line 357, referer: http://webmail.xy.com/services/portal/sidebar.php