[imp] Problem with text/calendar

[Otto Stolz]

Hello,

when trying to accept an invitation (MIME type: text/calendar),
I end up in an empty screen. The PHP error log says:
> [02-Mai-2007 10:28:48] PHP Warning:
>   parse_url() expects parameter 1 to be string,  object given
>   in /var/srv/www/htdocs/webmail/horde/imp/lib/MIME/Viewer/itip.php on line 202
> [02-Mai-2007 10:28:48] PHP Fatal error:
>   Cannot use object of type PEAR_Error as array
>   in /var/srv/www/htdocs/webmail/horde/imp/lib/MIME/Viewer/itip.php on line 205

What should I do to repair my installation?

Thanks, in advance, for any useful hint,
   Otto Stolz