Our kitchen TV is connected to the FiOS ONT via a basic digital adapter (Motorola DCT700/US). On some TV channels, the sound disappears and the picture freezes for up to a few seconds at regular intervals.
The problem affects only channels 11 through 25, as far as I can tell (I didn't try every single one!). It occurs at the top of every minute, at the instant when the on-screen clock display rolls over to the next minute. Sometimes the event lasts for only a second or so, in which case the sound resumes and the picture unfreezes after the interruption. If the signal loss persists for longer, I get a gray screen with a message that "the channel is having technical difficulties" before the program resumes. Either way, it's very annoying.
If I'm watching the same channel via the SD set-top box in the living room, or via either of the CableCards in the TiVo DVR, there is no interruption of sound or picture.
The DCT700 was installed and activated by the Verizon rep as part of my FiOS installation two weeks ago. I don't recall the problem showing up when he performed his final checkup before leaving, but it's possible we chose channels outside the range mentioned above and/or weren't watching the TV during the fairly short time interval during which the problem occurs.
I tried disconnecting the power adapter from the DCT700 for about a minute, but the problem was still present after the DCT700 restarted.