Router Does not Connect via ADSL Modem

Hi,

I have a wireless router connected to a desktop PC and an ADSL modem. I also have a notebook with a wireless connection to the router.

Until two weeks ago everything was working fine. Since then, though, I cannot get an Internet connection even though there appears to be no hardware problems. When I connect the modem directly to the PC it connects to the Internet.

What might the problem be?

Thanks in advance for your answers,

Frustrated!