ERROR UPGRADING FROM SNOW LEOPARD TO MOUNTAIN LION

HI GUYS,

I am using Snow Leopard and I just bought the installer from AppStore of Mountain Lion to upgrade my OS. After more or less 2 hours, I was able to finish downloading the installer. When I installed it, it says that the file cannot ber verified and it could be corrupted during the download process.

I tried to download it again but the CODE Apple sent me says it is already redeemed. Now I am stuck no doing nothing about it. I still have the file I downloaded to upgrade to Mountain Lion. I try and try to install it but getting the same error message. Apple is still not answering the right questions I have sent them.

Can I still use the original file I downloaded or do something about it?

These are the things I've done based on online forums to fix it but to no avail:

1. Repair Permissions via Disk Utility

2. Updated Snow Leopard

3. Rebooted and tried to install but still same error.

Thanks for your time and help