DIR 524 dlink router configuration problem


alliance broaband
I have recently bought a DIR 524 router of D-Link brand. My broadband company is Alliance broadband. A software person from the Alliance company came to my home and configured the router and set up a connection with password so that I can use internet on my PC as well as my laptop at the same time. It worked well for 3-4 days, however after that it started showing "error in connection". When I called the Alliance engineer, he said that there is no problem with the internet connection and that there is problem in the router. He also showed me that the internet connection is okay by connecting the broadband cable directly with the lan card. I want to know how to check the setting with the router and check where is the problem in connecting with the router? please tell me in details as i hardly know much about router connection.