can't be mpg, must be mp4, per the manual.
can't be wmv, which is what "wma video" is...
so basically, try converting to divx, burn to cd/dvd, OR try converting to mp4, then stick that in ur usb/sd.
i got an sd here, i'm gonna throw some mp4 vids I have, see if it works.
** EDIT **
Yep, works fine, cept it showed at 432x240, the original encoded size for my mp4 vid. . Suggest you go and encode to the max size of the player. Search what it is, it's everywhere here in the forum.