This indicates an attack attempt to exploit a Heap Overflow vulnerability in JustSystems Ichitaro Office.
The vulnerability is due to an error when the vulnerable software handles an Excel file with a malformed 0x3c record. An attacker can exploit this to execute arbitrary code within the context of the logged in user via a crafted XLS file.
System Compromise: Remote attackers can gain control of vulnerable systems.
Currently we are unaware of any vendor supplied patch for this issue.