This indicates an attack attempt against a Use-After-Free vulnerability in Microsoft Internet Explorer.
The vulnerability is caused by an error when the vulnerable software handles a used element's property. An attacker can exploit this by tricking an unsuspecting user into visiting a malicious webpage and execute arbitrary script code within the context of the application.
Internet Explorer 6
Internet Explorer 7
Internet Explorer 8
System Compromise: Remote attackers can execute arbitrary script code within the context of the target user's browser.
Refer to the vendor's Web site for suggested workaround.