Antifreeze question/problem

I just had the coolant flushed and replaced. I parked the truck after lunch today and noticed antifreeze dripping into a nice size puddle under the truck. i popped the hood and the coolant was leaking boiling out from the cap, the truck was extra hot too, but the gauge was not reading too hot. I guess the cap could just be loose, it was to hot to play with and I didnt have a rag at the time, but what else could be the problem?