Very puzzling… On my Mac the Hexagon Application is 90.4 MB. It might be worth checking what it is on yours in case something has gone wrong with the unzipping.
If Hexagon is in your Application Folder then drag it to the Desktop and see if it will run from there.
I’ve got Hexagon running on three different Macs all with different versions of OSX and under Mountain Lion it’s the most stable. If I do have any problems, trashing the Preferences is usually the answer but if it has never launched I don’t suppose it’s generated any.