Help! Minecraft wont work?

I cant get minecraft to run on my mac..its running 10.5, latest java. When I try to log into the launcher it says "user not premium" (not downloaded) BUT it is downloaded! it doesnt give me the option to play offline..its the beta, I havent boughten the game. I looked around through my system folders and found the "minecraft" folder was empty!. I reinstalled at least 10 times and still, it always downloads with an empty folder! Also, the minecraft launcher doesnt look right, it has alot of code written at the top and its all glitchy. I tried this on another mac running 10.5 too and it did the same thing! then, i tried logging in on the website to play in browser but it still says user not premium and that i need to buy the game! please help!