Short answer: you need to write a udev rule.
For some more information, you can see this link http://www.nabble.com/pvr-150-occasionally-swaps--dev-video1-to--dev-video0-td16358277s15552.html
It is also described in the MythTV wiki http://www.mythtv.org/wiki/index.php/Device_Filenames_and_udev
Such rules can be a little hard to understand and get working.
I don't know of other ways to solve it, but that does not mean there aren't ;-)