In the short term I'd try charging just 4 batteries at a time putting a battery. It's not a long term answer as you'll still need the upgraded plug to get the full charge rate.
I had a hiccup a while ago when my VC2 couldn't even charge 2 batteries at 0.5 amps lol. I remember taking the USB lead from my battery charger to charge my cheap crappy phone - I subsequently accidentally fitted the skinny USB lead from my phone that was rated to charge the tiny 1 Amp battery in my phone in about 3 hours lol and it couldn't provide enough current to the charger for 2 cells at half an Amp.
It came as a surprise to me as I assumed USB cables would be the same, but no they're not - make sure you have a decent cable to go with the plug or you may have another problem caused by the cable.