same thing happened to my xbox a month or two ago. it go struck by lightning, network port fried, wireless controllers can't sync.

same case like u; controllers can turn on the box, but after that it just won't connect. trying to re-sync the controllers to hte box using the sync buttons won't work as well.

i dont have solution but i can tell u this: changing the RF module won't help either. i did it already, still same symptoms. i'm assuming that the damage is on the main board itself, not the RF module. i suggest u get a new box or if ur box is still under microsoft warranty = send it back