Threads with "freeing items", "Sending data" and "Locked" never finish

In one of the servers we have an issue that happens to one of the servers that some items
that have the status of "freeing items" and "Sending data" are just stuck there, causing a
lot of locks on the server, and the load of the server drops to almost 0.

The server then wouldn't restart, and the only solution is to kill the mysqld process, and
fix the crashed tables that result from the kill.

How to repeat:
There is no specific knowledge of when does this happens or why, but it happens like once
every 3 days.

Solution:
turn query cache off.

to follow up see: http://bugs.mysql.com/bug.php?id=45544