If you have voltage on each cell but not the pack then I would suspect something else, perhaps the thermal fuse is bad?
Radio shack has the worst batteries, I'd bet the mAH rating on the Makita pack is much more than the radio shack cells. Also the batteries inside the Makita pack most likely are not consumer top but the spot welded connected type.
Search for places like Batteries plus who can rebuild the pack with new cells if needed, or is you determine the cells to be bad order them from someone like digikey or mouser who can spot weld them into the right config.