Have been playing for several months with no issues.  As of this week it now takes an exorbitant amount of time to load the game.  In fact had I not been distracted a few days ago I would have continued to think that it was just completely locked up.

In addition I am getting the "character failed to load" errors and in game performance has begun to stutter a bit despite there not being a large number of mobs or "animated" blocks.  

The worst issues however is the extended length of time it takes to load the game, load a world and save a world.