More info, please. What did you upgrade, and what kind of DSL modem do you have?

Try opening a terminal window as root and type adsl-setup. Give it the information it asks for, then try adsl-start. The modem lights should flash, and it should say "Connected!" If not, it will say "Timed Out!" If the modem lights don't flash, your system isn't seeing the modem for some reason. If they flash but the connection still times out, there's a problem with either the PPP protocol (most likely a module) or your login.