Doesn't sound like there's any prob with your Deans work. And you're right, you've voided any warranty by changing the conns, so that would only be a waste of time and money.

Have you chaecked the voltage? Some chargers will give you that error for lipo when the voltage is below 3v/cell. Check the voltage across the main power leads and if its below 6, thats prob the issue. Check voltage on each cell using balance tap and see if both are low or is it just one cell thats low?

I just got two 3S lipos from them and one had a cell that was 0.28v and gave me similar error when I tried to charge it. I was able to save it by charging it as a NiMh at 0.1a (was only a 1600mah) until voltage was back up over 9v. Stopped the NiMh charge and tried lipo again and this time it charged fine.

Bet you're looking at similar prob.