That gun is broken, period. Call your dealer and have him return it to Beretta for replacement. DO NOT SHOOT that pistol until it is repaired.
Buddy, I have never seen a slide crack like that before. The only thing I can think of is that the metal must have had a casting flaw in it. That happened to me once with a Beretta Model 70S in 380 - the barrel came with casting pits large enough to seat a primer, just over the chamber area. Beretta told me they magnafluxed each barrel and didn't find the problem before selling it. I told them that if the flaw had been cast it probably would not have been picked up in the magnafluxing. They agreed and replaced the barrel. Same thing could have happened to your slide but whatever you do, get it back to them for replacement.
HTH. Mikey.