Getting On The Net With LAN Connection And Router?

I'm having problems with my LAN connection and router.Although the LAN connection is connected and firewalled, the router is on with all the lights working, i cannot get on to the net. When I open my internet browser to go to a web page it begins to search for it, however then displays page cannot be displayed message and informs me that the server cannot be found or a DNS has occurred.Sometimes i get a bubble pop up saying limited or no connectivity.

Before the connection stopped working, my main computer was connected directly to the router and there were two laptops also using the router wirelessly. However now none of the computers can access the net The connection works if i remove the router and use a broadband modem.I cannot configure my router as no instructions came with it relating to its use and after numerous attempts at contacting the manufacturers