The mtd service is not starting at boot time. The file mtd.init.d in the ebuild needs the HOME environment variable set in it. The mtd.init.d files is installed into /etc/init.d/mtd Simply - add the line: export HOME=/etc/mythtv to the start() section, before the ebegin. I copied the HOME setting and value from the mythbackend service startup. mtd needs it too.
We might have to actually look at if we need/want to create some symlinks.
Fixed in mythvideo-0.22_p22864. Thanks for the report.