Server just hangs when executing a query

[Mayuran Yogarajah]

We had a bit of a scare yesterday when one of our scripts just hung
indefinitely.  We nailed it down to a query in the script.  When we
executed the query manually, it hung as well.  We ended up having
to restart MySQL which for some reason fixed it.

Some background: We're running MySQL 4.0.25.  Shortly before
this we shut down many of our scripts because we were taking a
snapshot for a replication slave.

Does anyone have any ideas as to why this happened, and why restarting
the server fixed it? I'm wondering if when we shut down our scripts one
of them had a lock open and the lock just stayed open.  This sounds far
fetched but I don't really have any other theories as of now :/

thanks,
M