[MC-20425] minecraft 1.6.1 world hangs

said worlds "work" for about 3 seconds before the game hangs. This only seems to be a issue with pre-existing minecraft worlds. I created a new world, and had no such issue

Client> 2013-07-01 14:01:52 [SERVER] [INFO] 2755287[/127.0.0.1:0] logged in with entity id 272 at (463.1905144845253, 73.0, -114.05654084038724)
Client> 2013-07-01 14:01:52 [SERVER] [INFO] 2755287 joined the game
Client> Setting up custom skins
Client> 2013-07-01 14:01:53 [SERVER] [INFO] Saving and pausing game...
Client> 2013-07-01 14:01:53 [SERVER] [INFO] Saving chunks for level 'Oceana'/Overworld
Client> 2013-07-01 14:01:53 [SERVER] [INFO] Saving chunks for level 'Oceana'/Nether
Client> 2013-07-01 14:01:53 [SERVER] [INFO] Saving chunks for level 'Oceana'/The End
Client> 2013-07-01 14:02:45 [CLIENT] [WARNING] Memory connection overburdened; after processing 2500 packets, we still have 2719 to go!
Client> 2013-07-01 14:03:45 [CLIENT] [WARNING] Memory connection overburdened; after processing 2500 packets, we still have 7158 to go!
Client> 2013-07-01 14:04:32 [CLIENT] [WARNING] Memory connection overburdened; after processing 2500 packets, we still have 9054 to go!
Client> 2013-07-01 14:05:18 [CLIENT] [WARNING] Memory connection overburdened; after processing 2500 packets, we still have 13288 to go!
Client> 2013-07-01 14:06:19 [CLIENT] [WARNING] Memory connection overburdened; after processing 2500 packets, we still have 18811 to go!
Client> 2013-07-01 14:06:19 [SERVER] [INFO] Saving and pausing game...
Client> 2013-07-01 14:06:19 [SERVER] [INFO] Saving chunks for level 'Oceana'/Overworld
Client> 2013-07-01 14:06:20 [SERVER] [INFO] Saving chunks for level 'Oceana'/Nether
Client> 2013-07-01 14:06:20 [SERVER] [INFO] Saving chunks for level 'Oceana'/The End
Client> 2013-07-01 14:11:01 [CLIENT] [WARNING] Memory connection overburdened; after processing 2500 packets, we still have 22629 to go!
Game ended with bad state (exit code -805306369)
Deleting