Problem with accessing OWA

Ok...we have had in place for sometime 2 email (exchange 2003) servers one a front end and one a backend.  Users have been able to access webmail with no issues.  We recently added a second backend server and migrated some of our users to this server (same domain).They still have the same email address and their email works fine using the outlook client but when the users who have been migrated to the new server try to access their email via webmail it bombs out.  The user is prompted to enter username and password once this has been entered...there is a long delay as the page tries to load then you get a an "page cannot be displayed". The users on the server that hasn't been migrated work fine accessing OWA.  And again...internally using the Outlook client the migrated users work fine.  Any suggestions? Please be specific because i am new to this environment.  It's also worth noting that if i try to access the new backend server directly ..http://dcexg01\exchange and enter the username and password (any migtrated user) it again bombs out. However if i do the same on the older backend server and a user that is still on the 1st server it works fine ..so is it a configuration issue with the 2nd backend server? Please help!! Thanks