Apparently the new patch caused quite a few problems for people with multi-core AMDs. These problems include hard locks (freezes) which don't allow alt-tabbing to windows and blue screens with the message "a clock interrupt was not received on a secondary processor...". After much trial and tribulation, the (temporary) solution is setting shaders to 2.0. This can be done in video options, under advanced and should be done before logging in with your character.
Here be thread on AoC forums: http://forums.ageofconan.com/showthread.php?t=11056&page=1
Here be thread on AoC forums: http://forums.ageofconan.com/showthread.php?t=11056&page=1