I wouldn't trust that charger to charge anything.
If that's what you have..maybe that's your problem?
Any 5 cell pack from any of the big manufacturers, Trinity, Orion, Peak, etc. will be fine.
Make sure you get a good quality Ni-MH compatible charger, like the Integy, Novak, LRP, or other units. They are much better for your batteries.
Make sure you charge only on Ni-MH mode, and at nothing higher than 1 amp.
Aaron Waldron - LiveRC