Outlook 2011 disconnecting from MS Exchange

It seems as without cause our Outlook is disconnecting from our MS Exchange 2010 account on SBS2011 server. It was work flawlessly up until recently. Following other Google posts it seems we are not alone.

Mail seems to be fine, although not 100% verified app.

Any insights or tests would be beneficial.

We know we can use remote email (OWA) and access is Ok, but only through Outlook 2011 fails.

Thanks.