Hi, I have apair ofExchange 2007 SP1 CAS servers (no Multicast NLB yet but working on it, using VMWare), published behind a farm of two physical NLB Unicast IntegratedISA 2006 Enterprise servers. On the ISA servers im using a listener with HTTP Auth (Basic and NTLM ticked)which delgates to the CAS servers using Kerberos Constrained Delegation. I have setup delegation on both the ISA computer accounts and each lists boththe CAS servers. When browsing around within OWAI get error messages with what seems to be anything Exchange Web Services related. OOF, Free/Busy and then just at random even if i leave the client alone (probably some background task) EWS seems fine internally using normal Outlook - I can do Free/Busy and OOF. The message is "Outlook Web Access encountered an unexpected error and was unable to handle your request." I don't even know where to start looking for logs to find more information. Has anybody got this setup, had this error messsage or can tell me where to look for more logging - windows event log and ISA alerts seem fine, no errors. As far as I can see - and testing has been limited. If i use Forms Based Auth externally there are no problems - but I want HTTP auth internally for OWA. All internal traffic is routed through ISA too. Mark

Bit more info here, i seem to be getting 400 errors in the CAS IIS log at the same time as the error, hopefully not a red herring as I cant imagine these are meant to be there. 2008-03-26 17:56:39 W3SVC1 SERVER-IP-REMOVED POST /OWA/ev.owa oeh=1&ns=CalendarView&ev=GetViewPayload&prfltncy=0&prfrpccnt=0&prfrpcltncy=0&prfldpcnt=0&prfldpltncy=0&prfavlcnt=0&prfavlltncy=0 443 domain-removed\username-removed ISA-MEMBER-INTERNAL-IP-REMOVED Mozilla/4.0+(compatible;+MSIE+7.0;+Windows+NT+6.0;+SLCC1;+.NET+CLR+2.0.50727;+.NET+CLR+3.0.04506;+InfoPath.2;+.NET+CLR+1.1.4322;+MS-RTC+LM+8) 400 0 0 Note the request appears to come from the internal NIC IP of one of the ISA server array members, normal I guess so the return traffic knows where to go (SSL Bridging). Anyone have an idea what this 400 error is about? Mark

Found the answer after logging a call with Microsoft PSS, http://support.microsoft.com/kb/945882 seems to fix this - installing the hotfix and then running the .vbs. phew, hope this helps someone else out.