Microsoft has released an update to their Office 2008 suite for the Mac. The update is listed as "critical":
This update fixes critical issues in Office 2008, including issues that might cause Office 2008 applications to stop responding or quit unexpectedly.
Microsoft Office 2008 was released at this year's Macworld San Franciso in January, and provided native support for Intel Macs for the first time.
A knowledgebase article provides a detailed list of fixes. Many of the fixes appear to address reliability and stability concerns.