tivo series 4 hangs up

I have a tivo series 4, about 1 year old

it is plugged into the wall outlet directly(that's what tivo.com told me to do when I told them this issue about 2 months ago)

I have a cable cord plugged in
a wireless netward adapater plugged in
an extternal hd plugged in

sometimes when I pick a new program to record, the tivo will freeze and nothing does anythingl

I still see the lights on the front of the tivo flicker when I press the TIVO button on the remote, the volume buttom still works, but the tivo stops responding
although if it needs to record shows it does or continues to do so

to regain control of the tivo, I unplug it, then plug it back in

how do I stop it from freezing on me?