What kind of broadband connection do you have?
Cable - connect to modem like previous poster said
DSL ? if you have 1) a newer modem with the PPPOE on it, then go straight to the modem
2) if you have an older modem where the pppoe is on the router, you may want to try some other things before doing this check.
1) change cables - its the classic "is it plugged in" ethernet cables can get flakey at the connectors
2) plug into a different port on the router. Switch ports on a router canports go bad, if this solves your problem just leave it plugged into the other port
3) try connecting wirelessly. If you have a router, its probably also a Wireless AP, so give that a try
Other things to check. Look at the routers connection status screen. See how long its been up.
And last, but really the FIRST thing you should do is reboot. REBOOT EVERYTHING. Router, modem, computer, ethernet attached printers.
Then turn them on in this order
1) modem
2) when you get a green cable or dsl light
3) turn on the router.
4) then all the routers dhcp clients (pc, mac, printer)
Hope this helps.
Don
p.s. another thing to do is to plug an old router in and see how it does. somebody you know must have an old B router around.