Error -42403

Last night my iMac messed up and I ended up having to restore it from a Time Machine backup, now I've got a few problems, like having to reinstall Skype, Mail getting confused etc.

But, I've got something worse, I want to watch a movie rental and it's not there, asks me to reconnect it, but I'm guessing the file's hidden or something. So I thougth I'd watch another movie and fix it later, and tried a movie which I bought (Not rented) and it wants me to authorize the computer again ^_^ so I do that and it comes up with an error, -42408.

My main concern is that when I open it, it comes up with -42403.

It also wants me to restore my iPhone.

How do I uninstall iTunes and reinstall it? Will it remove my movies? I've noticed that you can't redownload movies again which isn't helping against piracy, Apple. I wouldn't be surprised if it's literally impossible to retrieve a rental...I can't believe I even bother watching movies on iTunes anyway...

I'm running iTunes 10.6.1 and Mac OSX Snow Leopard 10.6.8, I've checked for updates as well.