Van keeps dying?

We have a 02 KIA Sedona EX, the van works fine and then just dies and won't start. Today we sat in the van with the key set to ACC so we could listen to the radio. After 5-10 mins I turned the key to start and everything died. The Van wouldn't start and I had not power. I had to unhook the negative battery cable for a second or two. After hooking it back up I had power again and I was able to start the Van. A few weeks before this happend my wife went to leave for work in the morning. She said the clock was off and all the radio persets are gone, as if the battery had died or been disconeted.

The battery is brand new I just got it last month, the connectors are also brand new.

I'm not the best with multi meters, so lay it all out for me.