In a brilliant maneuver no doubt designed to limit the load on their servers, Turbine has let their SSL certificate expire. There is a thread about the issue on the official forums. There is also a dev post. The problem will create SSL errors on the LotRO client and won’t allow users to log into the game.
The fix is to move the date on your PC clock back to 1/1/2009.
This fix will, however, cause issues with any daily quests.
Edit: The issue has been resolved. Turbine states that they did reup the certificate but for some reason, the original request didn’t take. A new certificate has been set up and the game should work correctly now.