open up backend2003setup.wsf.log.
Search from the top of the file for the string configureschema and the second instance of this string should be a line that reads:
Connected to: http://EXCH1/exadmin/admin/EV.Local/mbx/SystemMailbox{6E8989D4-6A8B-462A-B52DE6F92FC08EDD}/%
23%23SchemaURI%23%23
Copy the URL to the clipboard.
Paste the contents of the clipboard into the Exchange Store URL field and change each instance of %23 with # i.e. the end of the URL should now read ##schemaURI## and click OK.
In the left hand pane open up the KVS folder and click on the OWA2003Forms sub-folder
Mark