I'm using an HD TiVo with the factory HD, lifetime service, and a Cablecard provided by Optimum. Recently, the device has started behaving somewhat unreliably. The most common indicator of a problem is that I'll receive some channels, but I won't receive other channels (they'll appear black but won't show the no signal message). This happens every few days, but other times it's more-sporadic and will be fine for a week or two. A reboot (using the TiVo menus) or a hard reboot (by pulling the power cable) seems to remedy the problem, but I'm trying to diagnose whether the problem is my TiVo or possibly the cablecard. I haven't tried swapping out the cablecard yet (previous interactions with Optimum have been a combination of hostility/confusion regarding my cablecard use. The only way I could have them diagnose the problem would be to leave it in it's "broken" state after it occurs, schedule service, then have them come look at it a week or more later, which isn't really possible. I'd also like to avoid having them come service my signal only to tell me that the problem is my TiVo then charge me for a service call. I was wondering whether this symptom was an indicator of a hardware problem with my TiVo or whether the cablecard is the likely culpret.