can't connect to LAN

I live in a hostel where we are provided LAN ports to connect to the intra-hostel LAN, as well as internet, through a proxy.

all this was working fine but suddenly, since a few days, I can't connect to the LAN(or the internet). Its not a problem of the port in the wall, or the wire(since I checked all this with my friend's laptop, he can connect)
Either the socket on my laptop is not working properly(chances are less of that, it did work some days back) or there are some software issues in my laptop.
How do I treat this? What drivers to re-install?
Also, when my proxy DID work, sometimes, if the computer was on and I would insert the wire, it wont recognize my lan cable. It's like, it would recognize but wont work(just what is happening now, it does say its connected to an "unidentified network", but doesn't connect to either the LAN, or internet) So I would have to restart my laptop with the cable inserted and then it would work.

tl;dr -> Earlier, if wire was inserted into socket BEFORE switching the laptop on, it would work. Else not. Now, it doesn't work whatever I try.
I used the troubleshooter but all it said was that windows could not automatically detect the network's proxy settings.

Edit - Reinstalled Atheros drivers, didn't help.
To be honest, by mistake, once I did insert a USB stick into the LAN port, but it wasn't THAT deep that it would affect any circuitry, or so I guess.

PS - In the taskbar, on the network icon, there's a yellow exclamation mark with a triangle. I guess you know what I mean.

Edit - Reinstalled BIOS A05, didn't help.
Now I'm starting to get worried :S