This indicates an attack attempt to exploit a vulnerability in Microsoft Internet Explorer.
The vulnerability is caused by a failure to correctly handle script errors which can result in accessing deallocated memory. It may allow remote attackers to execute arbitrary code by sending crafted HTML objects in a web page.
Microsoft Internet Explorer 7 on Windows XP SP2, Windows Server 2003 SP1 or SP2, or Windows Vista.
Denial of Services
Arbitrary code execution
Apply patches (see the Microsoft security bulletin for details).