OWA breaks after moving mailbox to exch 2010

Question

All my users are on exch 2003. I build a 2010 CAS server, re-directed my webmail.domain.com name space to the new 2010 CAS server. That works fine. The
2010 CAS re-directs exch 2003 OWA to Legacy.domain.com – works great. (EX 2010 windows 2008 R2 and the exchange 2003 is on windows server 2003) CAS server running CAS and HT, separate win 2008 R2 server is mailbox server. My users are using the exch
2010 URL.. 
But as soon as I MOVE a user’s mailbox from Exch2003 to 2010, the users cannot open OWA. OWA logon just hangs while trying to login. users are able to login to their mapi sessions just fine. 
This is happening to all users, regardless of the domain they’re in. 
So far I’ve confirmed that permissions on the users accounts are set to inherit. 
I’ve added domain users group (domain\domain users) to the local users group – Did not resolve the issue
I’ve confirmed that domain users (in both Domains) have ntfs permissions to the OWA Virtual directory – Still having issues… 
What can we try next? 
Your help is appreciated!

Answer 1

Everything else on the CAS works fine i.e. Outlook anywhere, autodiscover, mapi, activesync, even OWA all seem to authenticate the user. then as soon as I moved the users mailbox to ex2010, all the above still work except Auth to OWA. The results of
your PS command:
[PS] C:\Windows\system32>Test-OwaConnectivity -MailboxCredential (get-credential kratos\jeremy.rouse) -URL
https://sd-ca
s01.wfinet.com/owa -TrustAnySSLCertificate | FL
WARNING: [10:26:05.081] : The test couldn't sign in to Outlook Web App due to an authentication failure.
WARNING: [10:26:05.081] : Test failed for URL 'https://sd-cas01.wfinet.com/owa/'.
RunspaceId                  : df22936a-484c-4458-8c52-47285f236aab
AuthenticationMethod        : FBA
MailboxServer               :
LocalSite                   : WFINET
SecureAccess                : True
VirtualDirectoryName        :
Url                         :
https://sd-cas01.wfinet.com/owa/
UrlType                     : Unknown
Port                        : 0
ConnectionType              : Plaintext
ClientAccessServerShortName :
LocalSiteShortName          : WFINET
ClientAccessServer          :
Scenario                    : Logon
ScenarioDescription         : Sign in to Outlook Web App and verify the response page.
PerformanceCounterName      : Logon Latency
Result                      : Skipped
Error                       : The test couldn't sign in to Outlook Web App due to an authentication failure.
UserName                    : jeremy.rouse
StartTime                   : 12/22/2010 10:26:04 AM
Latency                     : -00:00:00.0010000
EventType                   : Warning
LatencyInMillisecondsString :
Identity                    :
IsValid                     : True