New 2S Reedy LiPo out of balance

[Toon]

A few days ago, I bought a Reedy AS309 7000mAh 65C 7.4V 2S LiPo (from MB Models http://www.rccarshop.co.uk/index.php...v-2s-lipo.html). Friday night is my local club race night, and I have just got back from using the LiPo for the first time. The problem is, the cells won't balance. I always balance charge, and charged the pack at 6.0A (which is the highest my charger will do), but 1 cell charges to 4.2V, but the other cell won't go above 4.0V. The charger ends up just constantly varying the charge rate up and down between 0 and 0.5A, but the cells won't balance. I thought the cell voltages might even out through use, but after 4 charge/discharge cycles (through racing), the imbalance is still there.

Has anyone had experience of this kind of issue? Would it be worth trying a storage voltage discharge, then a slow balance charge at 0.5-1.0A to see if the cells balance out? Or, as the LiPo is brand new, shall I just contact MB and try and get it replaced?

Cheers