Hallo,
I have a very strange problem I use NTLM authentication to connect Outlook 2010 clients (sp1) to Exchange 2010 server (sp1). Outlock can connect to server via rpc and download new mails but after 30 - 60 seconds ask for password.
I also have problem when I try to expand Outlook Distribution Group or download OAB (via rpc).
When I test my connection through https://www.testexchangeconnectivity.com everything seems to be ok :(
Please help ;)