Happened a few times.
Something happens, you suddenly get the loading screen. Then the message appears on top, that "it may take a bit longer than usual". But the loading screen never ends. (Once I left it there for a good 10 mins, and did not finish "loading", restarted game instead)
However!
You can get back on pressing the option button.
(a friend of mine told me in voice chat that while I was raging over being stuck on the loading screen, he could see my character allright, standing in the game world doing nothing. This is how we figured it out that something's amiss, and it's just the loading screen acting up)
Later it happened to him as well. Same technique above solved it.
Just saying in case you've run into the same. Previously I had to restart the game each time.
Big fat Nord Dragon knight with a huge hammer. - Tank
Stealthy argonian witch templar - Healer (lowbie)