Are you using jaunty then? 0.9.4 should be enough for Knots, but you may need to use some other format if h264 isn't working. If n8x0 profile is working, you could try increasing its quality a little. Or install the extra-decoders package from extras and try the Browser-profile. Most sd videos should play with passthrough just fine too. If you can find your way to our irc channel, I'm sure we can find a profile that works.