My HD DVR keeps freezing and then going to a black screen. I have rebooted the router and HD DVR (by turning off and unplugged each unit for 30 seconds) on several occassions which seems to temporarily solve the problem. However, the problem continues. Also, if I only turn the power off to the DVR and then touch 'menu' to continue it keeps going back to a few seconds before the freeze and then freezing in the same spot even though I'm watching live TV. None of the other TVs or STBs in the house exhibit this problem. Does my HD DVR need to be replaced?