The remote host is vulnerable to a Denial of Service (DoS) attack.
According to its HTTP banner, the remote host appears to be running a vulnerable version of Ipswitch WhatsUp Gold, a network management application for Microsoft Windows. It is reported that versions up to and incluing 8.03 hotfix 1 are prone to a remote denial of service vulnerability when processing certain HTTP GET requests. An attacker may deny service to legitimate users by sending a malformed GET request for the 'prn.html' file.
Upgrade to WhatsUp Gold 8.03 Hotfix 3 or higher.