Backing up library to new drive cause dcorruption on all purchased songs, anything that I ripped from my cd's are fine

Itunes purchases transfered to an external drive, I purchased these files and I know that I can download most of the ones I have purchased of course but really?

Maybe we should just download them when we want to listen to them, i know I sound a bit harsh but after upgrading both my Mac Pro and upgrading to OS Lion, everything does not work as it should and well my 1st Gen MacPro rocks compared to the new ones I think. If I could send everything back and get my money back on all I have spent with Apple I'd do it in a heartbeat. No excuses just frustrating as ****, either way things are looking like that old movie "Demolition Man" when the world is governed by Taco Bell, well it will be Apple i'm sure.