I am not a network expert (please pardon my bad explanation), but this problem has made me very upset.
In my office internet is shared among 15 users with the help of a wireless ADSL2 router. Actually this router is connected to another ADSL2 modem/router (the main one), We all work on laptops having wifi cards. The problem is that the internet disconnects quite often. Although the router shows all the lights on and blinking but I think it is not able to supply or share the internet with all the users and hence disconnects.
One is able to surf when he switches off and then switches on his wireless a couple of times. All the nodes are being assigned IP addresses dynamically by the router.