I have internet but can't connect?

I can connect to the internet just fine when using firefox, I can browse pages with no issues. But for some reason when I open up Internet Explorer. It says it can't connect.

On top of that, anything I try to download always gets connection errors when I try to install it. Things like Google Earth say it can't connect to the server even though I have internet. Also when I try to upload images on most uploading sites. I get more connection errors.

I adjusted all my firewalls, including the one in my router. It still won't connect on certain things. The odd part is. It was all working fine before I left on vacation and my computer was off and no one had access to it or my router, but when I got back. It all stopped working.

I have ran anti-viruses, anti-spyware, and anti-malware programs and they found nothing. I have tried downloading other programs to help, but I can never get them installed because of connection errors.