Vertical Lines during HDMI (HDTV Question)?

I'll try to best explain the "problem" as best I can, although it isn't necessarily a problem as far as I can tell. yet.

On my CRT TV, I noticed two things when I fired up my PS3 through HDMI. One, the black screens (as in truly black, like before a game starts up, or when you open up the "quit game/system" menu) are brighter than they appear during Component mode; and two, I notice some small yet visible transparent lines going vertically from the left to right of the screen.

Again, the lines only appear when the picture is almost completely black, like before a movie starts and you get a black screen with text. And it doesn't seem to show up in the actual game or movie, even during nighttime scenes or other moments of black. However, the fact that the lines are there in the first place do bother me a bit. It has nothing to do with the system either, since I switched it to component just to make sure.

One method I found to countering the problem was to lower the brightness setting on my TV (which was set pretty high). This makes the black more solid and similar to how it would appear on component, and the lines are almost completely invisible too. However, I do wonder if these lines are common in CRT's in the first place, or if there might be something interfering with the signal. Does the TV's plug have anything to do with it? Would it matter if I had the TV plugged directly to the wall instead of an extension outlet or surge protector?

Again, not sure if it's something to worry about or if it's perfectly common. But I'd like to make sure either way.

Jam it back in, in the dark.