I have hundreds of BVH files and i doubt one of them actually works 100% with Poser. When a company does any sort of motion capture and sells it as a BVH it generaly means it is used for a few formats so not really being 100% compatable.
As pain staking as it sounds i take a BVH i like and then do all the adjustments needed though the wave editor. I never had much luck with python methods.
In fact i recently did my own motion capture avi (check out the video center "test walk") and got a brilliant bench mark for a walk cycle using the .avi as a background and just simply matching the poses. it took about a month to refine mind lol
Patience is the key, if it worked "out of the box" then everyone would produce great animations ;)
Good luck with your results.
V