I don't know if this will work.. but I think it might help. (I'm in Maya 2012)
Go to Window<Gerneral Editors<Component Editor
Then find the tab for smooth skin - Click on that.
Should show all the joints/bones by name.. you can set the weighting by hand here.. 0 is none, 1 is full or 100% or you can do something in between.
Good luck! Please let me know if it works.