The remote host is missing an update as announced via advisory SSA:2004-124-03.

https://secure1.securityspace.com/smysecure/catid.html?in=SSA:2004-124-03

New xine-lib packages are available for Slackware 9.1 and -current to fix a security issue where playing a specially crafted Real RTSP stream could run malicious code as the user playing the stream. More details about this issue may be found in this advisory: http://www.xinehq.de/index.php/security/XSA-2004-3