Glad you two posted this, I was just about to go into Myth and schedule updates. As that apparently doesn't work, I just created this file:
-rwxr-xr-x 1 root root 59 2008-05-03 00:35 /etc/cron.daily/mythfilldatabase
With this in it:
If mythfilldatabase should have additional flags, please let me (us) know.