From Zone-H.org:

08/04/2004

Description: A denial of service vulnerability was reported in the Windows Remote Desktop service in Windows XP and Windows 2003. A remote user can cause the target system to crash in some cases.

Nick Lowe reported that on systems with Remote Desktop enabled, a remote user can hold down the Windows Key and the "U" key simultaneously and continuously at the login prompt to cause the target system to crash. The key sequence reportedly causes the target system to continually load the Windows utility manager, which will terminate if another instance is detected. However, it is reported that on some systems, instances of Windows utility manager can be loaded more quickly than they are terminated, causing all available memory to be consumed.

According to the report, Windows XP SP2 appears to be not vulneralble. Also, higher-performance systems are not affected.

Impact: A remote user may be able to cause the target system to crash.

Solution: No solution was available at the time of this entry.

Vendor URL: www.microsoft.com/technet/security/

Cause: Resource error, State error

Underlying OS: Windows (2003), Windows (XP)

Reported By: "Nick Lowe" <[email protected]>
And here's some more information.