This indicates an attack attempt to exploit a Memory Corruption vulnerability in Microsoft Internet Explorer.
This vulnerability is a result of the application's failure to sanitize user inputs. As a result, a remote attacker can exploit this to cause a Denial of Service condition or possibly execute arbitrary code within the context of the browser.
Microsoft Internet Explorer 6
Microsoft Internet Explorer 7
Microsoft Internet Explorer 8
System Compromise: Remote attackers can gain control of vulnerable systems
Apply the patch available from the website.