1.7 clients freeze/unresponsive when breaking block with glass sound

Whenever breaking a block that uses the glass breaking sound file, for example, ice, glass, redstone lamps - The client freezes and becomes totally unresponsive. I believe it also happens when using splash potions too.

No matter how long you leave the frozen client it doesnt crash and produce a crash report - hence none being uploaded.

Java has been updated and the client has been re-downloaded.