Have 5 computers in the house. 1 can not connect to certain websites

[draexo]

I have five computers in the house. 2 laptops and 3 desktops. One of the machines is unable to connect to certain websites - one specific website is gradelink.com, which the school uses for grading and assignments. I connect to the site, however, regardless of browser (IE, Chrome, Firefox) when I hit login nothing happens.
If I use any other computer in the house or my phone connected to the same network via WiFi, I can connect and log in.
I also have issues with this computer where I can not log in to site A on Chrome or IE, however I can log in with Firefox. Again, this is specific to this computer only.
Any ideas? My next step is to format and start over. This is Win 7 64 bit.

Thanks

 

[ur6beersaway]

Check~http://windows.microsoft.com/en-US/internet-explorer/ie-security-privacy-settings#ie=ie-10

 

[draexo]

Check~http://windows.microsoft.com/en-US/internet-explorer/ie-security-privacy-settings#ie=ie-10

That might possible help with IE, however, I set it to default settings and no change. This would also not help me with why Chrome and Firefox are doing the same thing.

 

[Hawkeye22]

Check your antivirus software to see if it's filtering web sites. Temporarily disable it, then test the web site again.