When you say "is connecting to the network OK", can you actually access the router's Setup pages by entering 192.168.1.1 into your web browser? Can you access "shared" folders over the network in the PC that is 'wired' to the router?
If neither of these is possible, what makes you believe you are connecting to the network? After connecting to the wireless network for the first time, the settings are saved in a 'profile' in the PC so that it can connect automatically the next time. If this 'profile' has become corrupt, the adapter will fail to connect to the wireless network. Connecting to your friend's network isn't a problem because you are manually connecting for the first time.
Try deleting your existing connection from the WiFi adapter's settings so that you have to connect manually again, i.e. run the wireless adapter's software, scan for "Available Wireless Networks", find and highlight the one that matches your router's SSID (network name) and select the option to "Connect" to it. Once "Connected", the wireless adapter should get its IP address by DHCP from the router and you should have network and internet access.
There is a difference between the Wireless Network Adapter and Router communicating with a good signal and "Connecting" (as in "logging in") to your Wireless network.