Portal Appears to Be Missing Content After You Upgrade to SharePoint Portal
Server SP2
Microsoft Knowledge Base Article - 813101
support.microsoft.com/?scid=kb;en-us;Q813101

... SharePoint Portal Server SP2 includes a change that causes the
SharePoint Portal Server service (Msdmserv) to turn on directory browsing on
the portal folder as part of the workspace upgrade. ....

Note that you may have to do this manually in some instances, especially if
you get the "Add Content" screen instead of your main dashboard.