2003 Dodge Caravan will not start

Our 2003 Caravan died on us last night, the lights in the car come on, dome lights and the gauge lights but as soon as you try to crank the car the lights go off and the car will not start. We tried to jump the car and it worked after we got home we shut the car off and tried to restart and it would not start so we tried to jump the battery agian and it would not do anything. We have a tester and it said that the battery was good, I don't think that it is the alternator since the lights are on. When you have the jumper cables hooked to the battery the speedometer is pegged out.
Any help would be great!

try cleaning the cables and the battery post.And check where the battery grounds.And when you said "it would not do anything" do the lights work,any click comming from the starter or completely nothing?

Just needed a new battery I guess. Thank God that is all that it was.
But Thank You for your help!