A reader asked how changing a cable can fix a temperature problem - there are many ways that this might happen, and I'll try and explain it a little bit for the technical-minded. A DVI link has 3 serial data channels, one each for red, green, and blue data. A dual-link DVI device has 6 data channels. There is also one clock signal. Each of the 3 or 6 channels has to be synchronized to this clock when turning on the display - the signals may arrive slightly before or after the clock, and the monitor has to check this.
Now, temperature affects ICs dramatically. Cold circuits conduct electricity better; the signal changes faster, but this can also make the signal voltage go past its intended target (this is called overshoot), and then it can start oscillating around the desired voltage (this is called ringing). These effects might force the monitor to sync to the signal poorly, so when it warms up and the signals slow down, it loses synchronization with the signal. This is why turning the monitor off and back on or unplugging it and plugging it back in can help - the monitor resyncs while it is warm, and doesn't have any problems.

Now, a different cable can do a lot of things. Perhaps the green data channel is a little longer or shorter, causing it to be skewed differently to the clock signal, and the monitor syncs to a different part of the signal. Or, it can change the frequency of the ringing, or the amount of overshoot. It doesn't even necessarily have to be a higher-quality cable - any different cable might make the symptom disappear. However, the problem is still there - presumably that the syncing hardware or the green channel itself is poorly designed to allow the hardware to get out of sync in the first place. This is why I recommended getting the monitor replaced earlier - but, if you're already on your 6th, a bandaid might just be easier than a new monitor. My Apple 30" display did the same thing when I got it 2 years ago, but they fixed it when I sent it back later.

Anyway, this is a very unstable situation - any change in cable, display, video card, temperature, or even tweaking video card settings might fix it or change the manifestation. Apologies to the non-geeks whose heads are spinning.