Just in case you needed some tech babble about cables today:
An unspoken rule of thumb is that quality cables matter A LOT for analogue signals, and not so much for digital signals. With analogue, the quality of the signal is entirely dependent on how strong and clean the signal is. Everything gets interpreted 1 for 1, so if there's noise that gets introduced, it gets included in the signal. Crappy cables (usually weakly shielded or unshielded) allow cross-talk between the individual cables, as well as letting RF interference in from outside. Analogue distortion can be anything from the snow storm effect, washed out colors, changing colors, loss of sync (like you were experiencing), and a whole bunch of other things so sometimes it can be hard to tell whether the distortion is coming from the source, the cable, or the display. Diagnosing this depends heavily on exactly what devices you're working with.
With digital, as long as the device can interpret the 0's and 1's coming in clearly, then the signal will be 100% true to source, even if there's mild to moderate interference. It would take a lot of distortion or a long cable run to trip up a digital signal. Digital distortion is also easy to identify - non-working pixels will come in either black, red, or blue (there are others as well). Most monitors/LCD displays make this color stand out on purpose so you can easily see if there's a problem (i.e. you have a damaged cable or too long of a cable run). Digital is either on or off; working or not working (on a pixel by pixel basis).
Diagnosing digital display issues (from my experience YMMV):
1. If the non-working pixels are
true black and stay in the
exact same spot, there is most likely a problem with the display. (dead pixels) You're SOL unless you still are under warranty. Repairs can be costly.
2. If the non-working pixels are a
single bright color and tend to
move around with the image, there is most likely a problem with the cable. (correctly working display interpreting invalid info) For example, when my Gateway Monitor is receiving a bad signal, non-working pixels or lines show up as bright, true RED. Simple, replace the cable or use a shorter cable. Remember, this is only true with DVI and HDMI signals, as VGA and RGB are analogue.
3. If the non-working pixels are a non-black color (they can be "flickering" as well) and tend to stay in the
exact same place, then there is most likely a problem with the source (I had both a Wii and Xbox 360 that showed green and brown pixels where the GPU had been damaged from too much heat). You're SOL here too unless you're under warranty. Wii's cost around $75 to be fixed at the factory, I assume others are similar or higher.
These guidelines are pretty loose, as there is also a lot of variance between digital devices. If you're getting problems with the video, always check everything to make sure you know where the problem is for sure!
