Move Active Mailbox Database - Outlook Clients disconnect and say "Need Password"

Where is the CAS server? Is it a single server or a CAS Array? Or something completely different?

Yes, there is a CAS array.  It appears to operate just fine.  Note that this behavior occurs with a simple "Move Active Mailbox Database" command in the console and do nothing else.  Most notably, I am not bringing down the two CAS servers that make up the array.

I was simply checking the location of the CAS role that's all.

Are the servers and Outlook fully up to date, there was a DAG issue that was resolved in one of the Rollups, I cannot remember which one.  You should be on SP1 Rollup 2.

I'm in 14.01.0270.001.  I thought I was up to date, but apparently there was a new rollup on 3/7, I will try to add that one.

The link for the rollup on technet does not appear to work right now, so that will have to wait....

http://www.microsoft.com/downloads/en/details.aspx?FamilyID=413b8979-76b8-4be4-a18b-015d025eb368&displaylang=en

I'm having the same issue. Seems like the problem is related to Outlook switching to HTTP communication with the CAS-server during failover/switchover

When you make the other server active, outlook then think you are on a slow connection and tries  to connect over HTTP. And if outlook anywhere is configured to use basic authentication, then you will be prompted for password..

There is (at least) two possible solutions

1. Disable Outlook Anwhere (can be done through GPO - with a special adm template)
2. Configure Outlook Anywhere to use NTLM (NB! Not tested)

Neither is perfect solutions, since Outlook anywhere is wanted on laptops and NTLM is not easiliy implemented in a TMG/UAG solution.

Although, the comments that I received were meant to help me identify the underlying specific issue, in this case the solution was more easily solved by painting with a broad brush.  The reality is that mounting two new mailbox servers was done in a morning and they were cleanly created in SP1.