The router probably have the option of disabling wireless communication. Maybe you disabled wireless broadcasting when you started using cabled connection. A small thing that is very easy to forget after just a few days...
Open the configuration page of the router and re-enable wireless connectivity.
It's also possible that during the last month one of your neibors started using his own wireless home network and it conflicts with yours. Try switching to another channel.
Electro
August 2011