RE: new batteries not working ... PLEASE HELP!!!
Yes, your batteries sound like they are fine. That lipo should be at 12.6 fully charged though.
If one battery runs the truck and the others don't, then you just have to figure out what it different about that battery. What you are describing sounds like a connector problem since the stock battery works but the new ones don't. Another possibility is a wiring issue with the BEC.
About a comment you made above: the battery will always take its rated mah if it's fully discharged, even if there is a bad cell. The cells add up in a 3s setup to increase voltage, not capacity. Each cell is 1600 mah and 3.7 volts. When you wire 3 of them in series, you get 1600 mah and 11.1 volts. What probably happened was the battery was not fully discharged, which with a lipo is a good thing. Try not to ever run them all the way down to the low voltage cutoff.