This indicates an attack attempt against a remote code-execution vulnerability in Microsoft Visio.
The vulnerability is caused by incorrect handling of crafted tags in a crafted Visio file. It allows a remote attacker to execute arbitrary code by enticing the target user to open a malicious Visio file.
Microsoft Office Visio 2002 Service Pack 2
Microsoft Office Visio 2003 Service Pack 3
Microsoft Office Visio 2007 Service Pack 1
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the patch, available from the vendor's web site: