Thanks for your replies. I'll explain some more.
I am talking about an internet connection in my apartment (in Korea), not my work. I connect to the apartments internet through a plug in the wall. I don't have access to the main router.
My computer worked great for about three weeks until it suddenly stopped working one morning. The computer incorrectly said the cable was unplugged. I couldn't ping anything.
I thought it was a problem with the connection in my room so I called my isp and they sent a repairman. The repairman was able to access the internet and said the connection worked fine. He said the problem was with my network card.
Since I'm new in Korea I didn't know where to find a network card, but I noticed that I could still pick up wireless signals so I bought a wireless router. I configured the router with a friends computer (which was very confusing since the configuration was in korean) then tested the connection on my friends computer and everything worked great for her. When I tried my computer I still wasn't able to connect. I tried using a proxy (foxyproxy) on my computer and the connection started working. I can even connect without the wireless if the cable is plugged into the router.
So I can only connect to the internet as long as I use a proxy and a router.
I am looking into your suggestions. So far I haven't been able to find any malware. I'll also do the network troubleshooting. Maybe I messed up on the router configuration, after all the whole thing was in korean. But it was a new router and would it make any sense for my friends computer (the comp that configured the network) to work correctly if the configuration was wrong?
Thanks for the help and sorry for the length.