Found this solution here http://forum.maratis3d.com/viewtopic.php?id=59
If you open a BVH file in blender and the Key frames are missing. You can recover the actions by opening the bad bvh file in a text editor copy and paste the data into another bvh file that works. Follow the link above to get the exact instructions.
This solution will also merge multiple bvh animations into one, just like you would, using the blender NLA system.
MERGING BVH’s TOGETHER : Alternate method
▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀You can use a simple text file editor to merge bvh files, for example
let’s say we have two files : BVH1 and BVH2 ;
open BVH1 with any text editor and copy everything above “frame time”. take note of the total ''frames" (10 in the screenshot)
now, close BVH1 and open BVH2. paste the stuff from BVH1 at the very end of BVH2.
then change the total frame number (just below frame time) for example, if BVH1 is 22 frames, and BVH2 is 77 frames put frames : 99 in BVH2 file.
Well thats all for now