Update for Exchange Server 2003 SP2 (KB 924334)
Internet Explorer 7, which was released last week, can cause a little problem when used with Outlook Web Access (OWA). To resolve this issue, there's a new patch available to download for Exchange Server 2003 SP2.
"This update resolves an issue where the Outlook Web Access (OWA) form would stop responding when you compose a message using the S/MIME control on a client running Internet Explorer 7.0 and accessing a mail server running Exchange Server 2003."
Here are the links for the patch and for the corresponding KB article: