Problems connecting to a router

Good morning. I've installed Kubuntu(Maverick)+Trinity from your preassembledbinary distribution, to replace my old Fedora 8 - still retaining a KDE 3.5, with which Iwas very happy, instead of getting a KDE 4.x. All seemed OK, but,unfortunately, I am not able anymore to connect through wi-fi to the Linux system which was acting as my router to the Internet. The connecting procedure works if I configurethis wi-fi connection with fixed IP address and DNS address. It breaks at the IP configuration step if I configure this connection as DHCP-based (as I was used to). I did not changed absolutely nothing in the router configuration, so I was expecting all would have worked seamlessly. I realized that, with DHCP, the connection from router to Internet must be ok for all to work well, butit is certainly so, because I can access the Internet from the router's desktop. Do you have any idea of which the problem could be ?ThanksDaniele Manghi