troubleshooting Outlook logon prompt for users

Synopsis: group of outlook users homed on Exch2007 reported logon prompt issues. Users(who already logged in the domain) get prompted to login upon launching Outlook. In some cases, users login successfully, but receive logon prompts intermittently
Systems/Software Affected: Outlook 2007, Outlook 2010, Exchange 2007
Things to check on Exchange 2007 CAS servers when such issues happen:
1. Please note that Issue could be related to a reboot of Domain Controller. Confirm with AD team prior to troubleshooting
2. Issue is also likely related to Offline Address Book (OAB)
login to the Exch2007 cas servers and confirm the following:
1. launch IIS manager and under default website
2. right click OAB, properties, directory security
3. make sure integrated windows authentication and basic auth are checked
4. Go to Exchange installation folder, for eg E:\program files\exchange server\client access
5. Right click on OAB, properties, ensure that authenticated users is in the ACE and check to make sure the group at least read and execute right
6. If all the settings are correct, you are done with your checks. If not, make the changes and do iisreset /noforce from the command prompt
as part of the test, you can type this url to verify you can reach the OAB xml file;