hmm.. odd.. have you checked on which bone you have rigged it, and if it's even a bone.. rigging a geoset to certain helper objects can make a lot of the derp-ups.. you also can get rid of the helper objects by opening the .mdl of your model in notepad, replacing all 'Helper' words with 'Bone'. But be sure to exit the notepad and save on prompt, so it doesn't mess up the model. then after that, try re-rigging. I use mdlvis for that
helpful? oO