After running the client for more than 4 hours, me and a few others have been getting a sevear drop in frames. I will be going along at 60fps, then the game will slow down to 1-5 fps for a split second. It will do this every 30 seconds or so until I restart the client then it is fine for another 4 hours. I am using the stable client, even after re-downloading the client. It doesn't solve the issue.
This seems to be a bug with the client.