If you receive an error when opening forwarded messages (sent as attachments), uninstall Google Desktop Search or revert to the previously installed version.
Reports indicate that opening Settings, Options and removing the check from the "Use Documents and Spreadsheets to open certain file types" box corrects the problem without uninstalling GDS. If it doesn't help, you'll need to uninstall GDS.
More Information
If you use Outlook 2003 SP3 and have a large number of attachments or a large number of recipients on the message, see You cannot open an .msg e-mail message file in Outlook 2003 after you install Office 2003 Service Pack 3