Cant establish wireless connectivity in Mac mini

I have been using Mac systems for a while now but have never faced such a problem with it before. I have a Mac mini which is installed with Mac OS X Snow leopard on it. The Mac mini was running on MAC OS X 10.4 before the upgradation. I have a linksys wireless router through which I used to access Internet on my Mac mini but after the operating system upgrade I Cant establish wireless connectivity in Mac mini. It shows that the Wireless network is connected but I am not able to surf. As I am not a networking person, I am not able to solve the problem. Therefore any solutions/suggestions are more than welcome. Thanks in advance.

First check the configuration of the router. If the router is not configured properly then the devices will not be able to access all the resources of the network and hence may get disconnected. To check the configuration of the router, you will have to login to the router using the default IP address of the router. Once you have logged in to the router, open the configuration page of the router, contact the ISP and get the proper settings for the router. Check if the router is configured properly and if there are any changes to be made, do it and then save the configuration of the router and reboot the router.

The devices which are connected to the router using Wirleless connection are assigned IP address by the DHCP running on the router. If the DHCP on the router is not working properly then the router will not be able to assign IP address to the devices which are connected to it. You will have to disable the DHCP on the router and then enable it again. To disable the DHCP on the router, open the configuration page of the router and then disable the DHCP. Once the DHCP is disabled, you will have to log in to the router again. Login to the router again and enable the DHCP again. Once the DHCP is enabled again, save the configuration. Try connecting the Mac mini to the router and see if the Internet is working.

Check if the drivers for the network adapter are installed and working properly. All the devices which are connected to the computer require a set of drivers to be installed to work properly. Drivers are the mediators between the operating system and device. If the appropriate drivers are not installed then the device will not work properly. Therefore check if the drivers are installed and working properly. If needed then try and update the drivers for the network adapter. Hopefully, updating the drivers will solve the problem.

The network Interface card is responsible for establishing and maintaining connectivity with the network. If the Network card is not working then the system will not work properly. Every network card has a software interface programmed which can be used for testing. This port is called as Self test port. To check the NIC, ping 127.0.0.1 from mac mini and check the errors in data sent and received. Ideally there should be no errors in the data sent and received. If there is any error in the data sent and received then the Network card is faulty and needs to be replaced.

Most of the problems which are related to the MAC systems are solved by doing a PRAM reset. Sometimes the invalid entries get stored in the system memory. If the system memory gets flooded with the invalid entries, then the operating system then you will not be able to access the RAM which may lead to such problem. To clear all the invalid entries, you will have to do a PRAM reset. To perform a PRAM reset, follow the steps below :-
1. Locate the following keys (R, P, Option and Apple)
2. Press and hold the following keys while booting the computer.
3. Keep the keys pressed till 3 start up chimes are heard.
4. Release the keys when third start up chime is heard.
5. Let the system boot normally.