I've just got myself a Philips 42PFL5403 Full HD LCD telly and have it hooked up to a MySky HDi box via HDMI.  Fairly frequently, the picture appears 'damaged', with horizontal lines across parts of the screen.  I had been thinking that this was probably a TV fault or limitation, but it could also be a problem with the Sky box, too.  When playing a recorded programme, the imperfections are always in the same parts of the show, so they appear to be saved in the recorded files, or else the television is having trouble with the same bits every time.

However, I'm pretty sure I also saw the same thing with an upscaled DVD, but cannot re-create it again.  This points to the television or, maybe, the cabling.  I'm using Monster HDMI cables to connect each device.

Has anyone else experienced these problems?  What is the likely cause?

Thanks for your input and help.  :)