2 years ago I had cable TV with Comcast. I had a crazy problem, every 30 minutes all the TV's in my house would POP and the screen would go white, then gradually the contrast would come back and all would be well for about 30 minutes. This happened mostly early in the AM or later at night. It would happen much less often in the middle of the day when the techs would come out. I finally gave up shortly after buying a 42" plasma afraid that whatever was happening would damage my set, although Comcast assured me that my set was fine even though they had no idea what was happening. Comcast told me that it was most likely a power surge, so I had the power company come out, the only surge was with the televisions connected to cable. I went with DirecTV and never had that issue again. However every time it rained I lost signal which drove me nuts. A year later the neighbor was having trouble with their comcast service and when the tech went to check the cable at the junction he was almost electrocuted! Come to find out the house was not grounded and was pushing electricity through the cable back to the junction (that was shared by me at one time). I figured that was most likely the reason I was having trouble as well. My 2 years were up with DirecTV.......hello Comcast. We used the new cables that DirecTV installed for two of my TV's and split off the cable that comes inside for my internet for my 3rd TV. Guess what? The TV's that are using the DirecTV cables are fine, but the 3rd TV is doing the same thing as before! I called Comcast to come back out today but have no faith that they will figure it out, they will most likely just keep changing out boxes until I get tired and give up. Does anyone have any ideas? I have issues with the internet as well, and every few months they have to come out and exchange my modem, and I'm on my 3rd router in 3 years(Comcast does not supply the routers just the modem).

I'm not sexist, and I think broads appreciate that. ;)

Just kidding of course. It sounds to me that you have a grounding issue. It might be prudent to have an electrician in to determine if your house wiring is indeed grounded adequately. He, or she, will be able to determine this by visual inspection and a few measurements. What could be happening is that you have a ground loop between the cable and power ground. That is, the grounds are not common and there's a voltage differential between the two. The symptom you have can be exacerbated by improper termination of the coax cable leads too. Had this in my new place where the twist-on connectors had no electrical connection between the shield of the coax and the barrel of the connector in four places.

If you are handy with an ohmmeter I can explain how to check this if you like.

My Dearest Jaguar (if I may address you as such)
You may be on to something. I just had Comcast come out. First the guy says, "I think the box is bad". So I gave him the history and he went outside to check signal strength. He said it was too high. I explained that last month it was too low for the internet to work properly. So he replaced the cables on his meter and plugged it in to an outlet...now everything was normal. However my system still failed, but he was unable to tell exactly what failed. He left without resolution. I am supposed to call him tomorrow morning when the problem should be at its peak (perhaps he's going to roll the idea around with someone else first). I was thinking if the neighbors house was ungrounded, perhaps mine is too. But your ideas which are based in fact instead of guessing make alot of sense. I'm going to call the power company out. The only thing that still makes no sense to me is...........when hooked up to DirecTV I had no problems, the very day I go back to Comcast the same problem raises its ugly head. Thank you for your insight, I'll let you know what they find.
PS
I'm a broad from South Chicago, I think it's a term of endearment ;)

DirectTV is satellite so there's no possibility of a ground loop through a cable TV connection. The cable and house could both have good grounds, but if there's voltage between them that will cause the problems - and even electric shocks.

Remember from science class when you made a battery out of a lemon? You stuck in two probes, one copper and the other zinc. Ground rods come in copper and galvanized (zinc plated). If you have one of each, and your ground is even mildly acidic you'll get a voltage potential between the two via galvanic action.

Donnyjaguar, Comcast has been at my house 3 days in a row. Here is the result: We removed the HDMI cable and are using component cables. This seems to have cured the problem with a slight exception. Now every time I turn on my TV the screen is blank but the voice works, so I have to cycle though the inputs back around to component2 which is where they have installed the cables. Then the picture comes in. Comcast insists that my TV is bad even though the same morning they installed their stuff it worked fine with DirecTV. I plugged my DVD player in to the HDMI port just to check, and I have no problems, so the issue must be with Comcast. I'm thinking of dumping them again, what are your opinions on Dish Network?

I never heard any complaints about DirecTV....

Yeah, both houses need to be grounded properly, but I don't think that's the power company's responsibility. They, being a monopoly, might be able to tell you the problem without charging you, but you'll likely have to hire an electrician to solve it, and if the work needs to be done next door so voltage problems there don't affect the cable signal coming to you, it could get dicey.

That first symptom also sounded like a cable amp's power supply having an intermittent problem. Did it happen at some particular temperature, so it was more in the winter than the summer, or morning versus midday, or the like? A client of mine had a bad dish that became good after the sun shone on it for a half hour or so!