There's nothing client side that should freeze unless your pc is generally overloaded and flash is being an issue.

You can get disconnected by the server if you don't regularly send a data packet. Basically behind the scenes even if you're not chatting it sends a "hi I"m still alive" packet. If that doesn't get sent for whatever reason you get dc'd by the server.

Try typing /ping in chat and seeing if you're massively delayed

N.B. How long have you waited after a freeze to see if it eventually unfreezes?