No programs at all with connect to the internet.

[Penguin Ninja]

I have an Acer laptop. Before this problem started, I used both the wireless internet I freeloaded off of some random person in the building and the private cable internet in the bedroom, whichever was easier. I know there is nothing wrong with either internet service because I am currently using the cable connection a different, slower computer, and the cable and wireless both worked fine on the laptop hours before. The reception sucked that day and I kept getting disconnected from the wireless. Suddenly, I got a message saying "Another computer has logged in with the same IP address" and was disconnected.
I recconnected, but none of my programs (Internet Explorer, Windows Update, Norton Antivirus, Guild Wars) could access the internet. (the network and sharing center says that I am connected to the networks but not the internet. The tools in the bottom right corner say I am connected to the internet.) I tried using the private cable connection, with the same results. The wireless intenet said there was something wrong with my DNS (i still barely have an idea what that is), and the cable had a similiar but different message. And yes, my window's firewall is off... which itself might be a problem.

I have tried:
Flushing my DNS cache.
Deleting all my cookies.
Deleting all my temporary internet files.
Scanning for viruses (though my norton desperately needs to update)
Tried to automatically obtain the new IP address (on cable)
Tried to renew something I forget about something about (on cable)
I even tried to Restore my computer to different days, but each time an error prevented it from completing.

Things that I did that day that might have caused a problem:
I viewed an attatchment of a powerpoint slideshow from a friend.
I downloaded and installed updates.
The reconnecting did not seem to be doing anything so I manually told it to reconnect.

I have tried looking about everywhere and no one else seems to have this exact problem. Please help.