This indicates an attack attempt against a heap overflow vulnerability in Remote Desktop Connection.
The vulnerability is caused by an error when the vulnerable software Activex Control handles a malicious property assign. It allows a remote attacker to execute arbitrary code via sending a crafted web page.
Windows XP Service Pack 2
Windows XP Service Pack 3
Windows Vista Service Pack 1 and Windows Vista Service Pack 2
Windows Vista x64 Edition Service Pack 1 and Windows Vista x64 Edition Service Pack 2
Windows Server 2008 for 32-bit Systems and Windows Server 2008 for 32-bit Systems Service Pack 2*
Windows Server 2008 for x64-based Systems and Windows Server 2008 for x64-based Systems Service Pack 2*
Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply patch, available from the website: