Movie size (height) not correct

When using Vidomi with XviD-Codec to encode and try to watch the movie with BSPlayer, the height of the movie is not correct, it seems to be half of the real height.
When encoding with DivX, I don't have that Problem.
I tried to watch an other (older) film encoded with XviD-Codec, which I know was displayed in correct size. Now it is also played with the wrong height.
Just tried using the Vidomi Player, the height of the film is correct again.
Anybody knows why this is so ?

Sorry for my english, but I hope you know what I mean.

Thanks