Are you still using your WRT120N router, IzBialek? If yes, I suggest that you configure the wireless settings on your router. First, is your wireless connection secured and password protected? Are you able to access the router page using router IP Address (default 192.168.1.1)?
If you are able to access the router page using the router IP Address, click on Wireless tab > Wireless Security sub tab and set the Security mode to Disable. Click on Save Settings button after the changes. Your network will be unsecured so I suggest you try connecting wireless to your router without the cable connected to the laptop. If you'll get internet access while the network is unsecured, a possibility is that your devices are having a hard time accessing internet with your secured network.
Another workaround is to change the router's SSID under Wireless tab > Basic Wireless Settings sub tab > Manual option. Use a simple SSID using letters and numbers only. Then, delete your old network name on your computers and connect to the new network.