Wireless stopped working

I have a Lenovo 3000 n100, which has a hardware switch for wifi/bluetooth. The switch is on, but wifi is suddenly not working. Rebooting doesn't help, nor does tuing the switch on/off, or disabling and re-enabling network or wifi. The wifi light is not lit (bluetooth is). In Lubuntu, the error is Wifi device not ready.

I'm not sure what to check next. The wireless has worked for the last 6 months, and I have not made any changes to configuration or software (unless maybe an automatic update happened without my knowledge).

Thanks!