If the problem was in the TV itself you'd see it on more than just your PS3, unless of course it's just something you've not noticed in other situations....though from what you explain it sounds like you'd have noticed it before if it was there.
That leaves the PS3, the cable, or the power supply. I really have no idea if the PS3 could cause this or not, but an easy way to find out is to hook the PS3 up with the cables that came with it and see if it's there. If it is then it's possible it's the PS3.
It could be a bad HDMI cable though, have you used that cable with anything else? Any problems?
Power being back fed due to a cheap and/or malfunctioning equipment ([ie] wall outlet / power bar/ outlet adaptor / bad ground in TV or PS3) can cause strange issues as well. Try plugging the PS3 in somewhere else, a wall outlet preferably as opposed to a power bar/outlet adaptor.
Like previously mentioned if you can take your exact same setup and try it on another TV that will also help point you in the direction of the cause.