little while ago my 4900 started to lock up, won't power off, if power off won't turn on. I had to reboot to make it work then problem again both wired and wireless. thats where I found it was my cec settings on 4900 was causing issue. then I turn off cec settings and ever since its been good. maybe you can give a shot to cec and leave it off on box and see if that helps.