Rails, MySQL, OS X, pain

This is purely a plea for aid, and nothing more. I have Ruby 1.8.2, Rails 0.13.1, and MySQL 4.14 running under Mac OS X 10.4. I have a simple Rails application that works fine, except that most of the time when I try to perform an operation that uses a database transaction, WEBrick hangs. The only way to stop it is to use kill -9 or restart MySQL. Usually the output in the log looks something like this when it hangs:

Question Columns (0.006397) SHOW FIELDS FROM questions
SQL (0.000621) BEGIN
User Load (0.007152) SELECT * FROM users WHERE users.id = 1 LIMIT 1

I can’t connect to the running process with breakpointer and use of the MySQL show processlist command shows that the database connection WEBrick is using is idle. Anyone Rails experts have any ideas here? Exhaustive searches of Google and attempts to seek help on the Rails IRC channel have proven fruitless this time around.

I should also note that the problems are intermittent. I can update or insert some rows in some tables some of the time, and other times things seem to work.

Update: Running the application under Locomotive works, so the problem must be something with the Ruby install on this computer. That’s one problem with any complex Web application these days — too many moving parts under the hood.