Channel 1 on 2.4GHz... dead?

Hi to all. I am facing the following problem: it appears that all of a sudden, when I choose channel 1 on the 2.4GHz band, there is no transmission, i.e. even as close as 1 meter from my router (RT-N66U) I have no signal. Going into the setup of the router everything appears to be working OK. Changing the channel to 2 or above, the signal comes back!
Any ideas? is it a hardware problem?
Thank you in advance