i am having the same problem now on a 2nd pair of these headphones.
They wouldn't turn on after work one day just under a year of owning them, I sent them back to the Canadian distributor, Gentec International, and had to wait about a month before they sent me this brand new pair. You can imagine I did not want this to happen again so I have been babying these things only to have the exact same power button failure problem not even a month after getting them.
I am waiting on a response from Gentec now as to what I should do, I sure hope I dont have to go another month waiting by sending them back and I love the sound on these headphones so much I dont want to switch brands,,,,,,
First world problems i guess...