For some channels, when I tune to the channel, everything is fine for about 5 seconds, then the screen goes black. There is still audio. I've seen this happen with Syfy, Spike and FX, both in HD and SD. Screen comes back when I switch to another channel. I got Verizon FIOS about a month ago. Other HD channels have no problem. TV (Samung UN55ES7150FXZA) about 6 months old. This did not happen with previous provider (CableVision - Optimum Online). Using HDMI connection. Any ideas? Need more info? please let me know. thanks.