Okay, so maybe all of the bugs are not quite worked out yet:
We have three Exchange mailboxes along with an Internet hosted SharePoint Calendar in Outlook 2010.
The hang up was on the SharePoint connection not throwing up an authentication window. It took a couple of shutdown and restarts before the credentials window finally showed itself.
The above was seen after Outlook mysteriously quite sometime between just before lunch and this afternoon when this post is being written.
How did we know? The client side rules were not being honoured and the Inbox was getting quite full. There are no indications in the system logs as to what caused it to stall either.
Microsoft Small Business Specialists
Co-Author: SBS 2008 Blueprint Book