A couple of hours ago my Outlook at work stopped working getting stuck on “trying to connect”. The Exchange Server appeared to be alive. Restarting and rebooting did not help.
I managed to unstick it by going into File -> Account Settings -> Account Settings (button) -> Double click on account -> More settings -> Security -> Always prompt for logon credentials (wow, what a way to structure the settings dialog!).
Next time the Outlook ran it asked me for user name and password, I entered them and voila – now it can connect. After that I went back to the same setting and unchecked the box.
The weird part is that it did not give me “invalid credentials” prompt, it would just hung.