Hi Gabriel,
I appreciate your efforts to resolve the issue and thank you for the detailed description.
Have you made any changes to the computer prior to the issue?
Looks like there is a server issue in the computer. Please follow the methods to fix the issue:
Method 1: Clear DNS cache
Your DNS cache stores locations (IP addresses) of webservers that contain pages which you have recently viewed. If the location of the web server changes before the entry in your DNS cache updates, you will be unable to access the site.
a. Type Win + R on the keyboard
b. Type the following in the Run text box: ipconfig /flushdns
Method 2: You may try to reset the TCP/IP stack go to this article and either click on "Fix it for me" or follow the instructions to fix it yourself:
http://support.microsoft.com/kb/299357
Method 3: Temporarily disable security software and firewall settings and check if the Internet Connection drops.
Disable antivirus softwa re
http://windows.microsoft.com/en-US/windows-vista/Disable-antivirus-software
Turn Windows Firewall on or off
http://windows.microsoft.com/en-US/windows-vista/Turn-Windows-Firewall-on-or-off
Note: Antivirus software can help protect your computer against viruses and other security threats. In most cases, you shouldn't disable your antivirus software. If you have to temporarily disable it to install other software, you should re-enable it as soon as you're done. If you're connected to the Internet or a network while your antivirus software is disabled, your computer is vulnerable to attacks.
Method 4: Refer to the articles:Wired and wireless network problems
Troubleshoot Internet connection problems
http://windows.microsoft.com/en-CA/windows-vista/Troubleshoot-Internet-connection-problems
Please perform these recommended steps and post back if you are still experiencing the issue. I will be glad to provide you with additional options.