If you get corrupted tables or if mysqld always fails after some update commands, you can test if this bug is reproducible by doing the following:
Take down the MySQL daemon (with mysqladmin shutdown).
Make a backup of the tables (to guard against the very unlikely case that the repair will do something bad).
Check all tables with myisamchk -s database/*.MYI. Repair any wrong tables with myisamchk -r database/table.MYI.
Make a second backup of the tables.
Remove (or move away) any old log files from the MySQL data directory if you need more space.
Start mysqld with --log-bin. See Binary log. If you want to find a query that crashes mysqld, you should use --log --log-bin.
When you have gotten a crashed table, stop the mysqld server.
Restore the backup.
Restart the mysqld server without --log-bin
Re-execute the commands with mysqlbinlog update-log-file | mysql. The update log is saved in the MySQL database directory with the name hostname-bin.#.
If the tables are corrupted again or you can get mysqld to die with the above command, you have found reproducible bug that should be easy to fix! FTP the tables and the binary log to ftp://support.mysql.com/pub/mysql/secret/ and enter it into our bugs system at http://bugs.mysql.com/. If you are a support customer), you can also <support@mysql.com> to alert the MySQL team about the problem and have it fixed as soon as possible.
You can also use the script mysql_find_rows to just execute some of the update statements if you want to narrow down the problem.