Cannot Install Disk Image

[Phaedrus]

I just downloaded the Penumbra Collection to my new Macbook Pro 15 inch and the disk image won't load! I literally just bought it and downloaded it direct from the frictional store. I did the same with Amnesia which opened and installed just fine. When I clicked on the Penumbra dmg though, it popped up a message saying that it did not recognize the disk image and then closed out. Anyone know a way to solve this problem?? I can't install the patch without having the collection of course, and I have no idea what to do!