does your export biped match the models one?
i use this method to export
1)create char file with mesh and biped , making sure all xforms are reset, model in T pose
2) make sure this T pose is saved as a max file at this stage and create the hero character folder
3) load the bip file to the max scene , and resize the frames bar to encompass all the frames but no more
4) under hero export , choose vda method , make sure the ticks are in the right boxes (repos to 0,0,0 is useful)
should also see exclude meshes is ticked and your ready to export
5)write a asq file for the animation hgm file
6)upload to engine and test animation by possessing the char and using
behave 0 anim * your_animation_name
in the console screen
hope this check list helps you , if you create a new animation bip just load the max file from stage 2 and follow the steps as normal