Local Area Network doesn't have a valid IP configuration

A few days ago I arrived to Germany to a study for a semester. In the house where I'm staying there's a modem with a Lan Cable that I'm supposed to use. I plugged it the day I arrived and I notices I had no Internet connection. After running a few diagnoses the system told me that "Local Area network" doesn't have a valid IP configuration. I don't know why this message appears and why can't I connect to the Internet. I've checked so many forums and I'm starting to believe there's no solution to my problem.
I've checked that the IP is in automatic configuration and I've also tried to connect with other modems what I obtain the same result....
PLEASE HELP ME, I will fail all my courses without Internet

You might need to power down the laptop, then power off the modem. Keep the modem powered off for about 30 seconds then power it back on. let the lights cycle through until you see connectivity on the modem, then (After plugging the ethernet cable into the LAN slot) power the laptop back on.

If it still doesn't work, you may want to check for Antivirus/Security software/Static Ips.

It doesn't work, what did you say about antivirus?

Some antivirus softwares my conflict with new ack requests to dhcp servers (your modem in this case).
Simply disabling it may not help, however. What antivirus and security sofware(s) are you running?

I'm running the Mac Affee and supose the security softwares from windows

If it were me? I would uninstall mcafee and related security suites then try again. once successfully connected, I would reinstall antivirus.

Can you try Irene's suggestions before continuing?

Irene[s suggestion didn't work. I can't reinstall mac Afee because I don't have the driver here I'm studying far away from home. Could it be any other possibility?

You're plugging directly into a modem without a router? Try the computer via wire at a different location. Try changing the wire. Disable McAfee in MSConfig/Startup (or lose it altogether and switch to MS Security Essentials, free). Open a command window and enter ipconfig /all > %USERPROFILE%\desktop\ip.txt and attach the output file here.

I dont think it's my mc affe I think it's a problem with the network on my student residence. If I buy a router and turn the connection into a wireless ocnnection. Will it work?