We have Verizon FiOS internet and TV service. We've had it for years now and love the speed of the internet and the relative slickness of the TV and DVR guide service.
However, I love to push the envelope so I've set up a few Windows 7 PCs with Media Center to use TV tuner cards and a Silicon Dust HDHomeRun network tuner. These tuners can either get over-the-air ATSC content or Clear QAM digital cable channels. They can't get encrypted digital cable channels (that will be solved by the upcoming HDHomeRun Prime network tuner or the existing Ceton card). Most cable providers only allow the local channels and maybe a few extra channels, like the Weather Channel, via unencrypted Clear QAM.
In any case, this was a supplement to our regular FiOS DVR and cable boxes so it has never been a priority. That said, I always like things to work properly.
Alas, when using the PC tuners to get ATSC OTA content, I could never get a consistent signal via antenna because of the location of our house. We get horrible cell phone reception and even radio reception is so-so. Digital TV reception has been less than desirable.
So, since we already had FiOS TV service, I had tried using the Clear QAM feed over the coax cable to get the local channels in Windows Media Center. Almost immediately after setting this up, weird things would happen. After a few days, channel 5.1 and 20.1 would switch, as would 4.2 and 50.3. Other channels would switch seemingly at random intervals. Different PCs in the house would have different channel mappings. It all seemed so random.
After searching the Internet for a solution I finally gave up for a while and went back to the antenna. But a few months ago I had enough and decided to figure it out once and for all.
I did some digging and the issue was NOT Verizon. The back-end Clear QAM channel numbers never changed. You can find the Clear QAM channel mapping on sites like SiliconDust. If you manually enter the channels in the settings, the channels never change.
After some trial and error, I found out that it was the Windows Media Center guide update and scanning process that was screwing them up for some reason.
I found the solution. Here is a recent post about it:
Also see: http://www.technixupdate.com/disable-stop-or-block-mcglidhost-exe-from-running/
Basically, you need to disable the BackgroundScanner. For the most part this works fine, except if you need to rescan for channels. In which case you can re-enable it.
In the Registry Editor, go to HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Media Center\Service\BackgroundScanner.
Set the PeriodicScanEnabled DWORD value to 0
The SiliconDust HDHomeRun software for Windows has a checkbox in the settings to do this for you. If you have another tuner card you can edit the registry as mentioned in the link above.