Website thinks I'm another computer......

I currently have an account with a website that has a lot of security. Whenever I log in, if I restart my computer and try to re log in with a few hours it says that I am logged in under another computer and can only login with one computer at a time. I talked to the owner and he said that it was added security and he doesn't know why it says I am logged in under a different computer even though I am not. This only happens when I restart, when I don't restart I never have this issue.

Does anyone know what could be happening to my computer and how I could fix it?

 

That sounds like an issue I've seen reported with a piece of software that needs to login to a secure site/server before you can use it, it appears to only affect users with Windows 7. I think the site uses some kind of hardware ID fingerprinting that can sometimes changes when W7 is rebooted, I really haven't seen a definitive fix for that site.

You could always try removing all cookies pertaining to the site in question before logging in? It doesn't sound like the right fix in this case though.