critical battery error

Hi all, I've been getting the two warnings which is a real nightmare I have 3 days of shooting later this week. One of them is a really good client so need to sort it out asap... I have been using 5 batteries and had errors on 3 of them so thinking its not the batts... I had two good flights...

I am wondering if anyone has seen this problem, I have not updated my remote to the latest firmware 1.7.4 until today, but right after doing so I was flying, draining down some batteries but, right after take off with 60% of battery power in the tank, immediately the copter when into critical...