In my organization everyone uses the Outlook 2010 connector to access the CRM.
After the UR13 update, but not right away, some clients began experiencing a situation where the Outlook connector asks for login every time they double-click an entity in a list, thus when opening a new window. It's the typical ADFS login form, displayed into the new window in place of the entity they chose to open. Sometimes also opening a list (e.g. Accounts, Activities, ...) causes the login form to be displayed embedded into outlook's center frame.
Either way, the credentials entered won't stick and in many cases a reboot is necessary. Sometimes I have to un-configure and re-configure the org with the Configuration Wizard to make it go away. But after a while it strikes back.
Unfortunately our setup is not a very standard one - the CRM-running machine (2008R2 all patched) is on its own domain in the same network with our primary one... which is incompatibly samba3-based. All users are mirrored in the two domains. Though I feel this is not the culprit.
Anyway, we've tried everything, from adding even junk to trusted sites, messing with IE settings, storing passwords in vault, fiddling with IIS authentication providers - no way. We're at stand still.
ADDENDUM: I forgot to mention that sometimes when it's not working we get a dialog saying "Waiting for a page to load from the CRM server", and a slow progress bar that smells timeout'ty (but the CRM is responsive via web). When it closes, the contents of Outlook's CRM ribbon is replaced by a string "A page failed to load from the server", or something along the lines.