If you find that your MythTV recordings freeze when you try to skip ahead, or if ad-skipping is broken, you can do this to fix the problem - at least for future recordings.
You need to have phpMyAdmin installed on your HTPC. If you don't, and it's a Debian based installation, use
# sudo apt-get install phpmyadmin
Select Apache2 during the auto-config stage.
And then set up a symlink between /usr/share/phpmyadmin and /var/www (or whatever your Apache root directory is - mine's /var/www) using
# sudo ln -s /usr/share/phpmyadmin/ /var/www/phpmyadmin
You might need to configure your MySQL root, too. Set a password for the MySQL root (not your normal root) using
# mysqladmin -u root password "PASSWORD"
(replacing “PASSWORD” with the password of your choice).
You should now be able to browse to your HTPC from a computer on your network. Visit http://htpc_name/phpmyadmin and log in with username “root” and the password you chose earlier.
Click on the “mythconverg” table to the left, wait for it to load in the frame on the right, and scroll all the way to the bottom. Click “check all” and then select “Repair” in the drop-down list to the right of “Check all”. Repairing may take a while, so let it run. Repeat “check all” and then select “Optimise”.
You should now be able to skip/search in any new recordings and, from some testing, any recordings done before the table broke. But probably not the ones you did while the recording was broken.