Does the HDMI cable length contribute to overheat the HD300?

[routerunner]

Folks, I'm going to post my personal experience on this, please take it as it is as I haven't found an explanation yet.

One of my HD300 did always run particularly hot when operating and slightly less hot when powered off (via red button on remote). I have to say that the hot level never alarmed me that much to justify adding some fans as some of you did, but hot enough to find it strange. The HD300 in question was connected via a 50cm QED Signature HDMI cable to the TV, but one day I needed that short cable for another project with another HD300 so I replaced it with and equivalent grade cable this time 1mt long. Well, since then the HD300 runs at least 50% cooler. I asked to one of our HW engineer at work regarding a possible plausible explanation on this and he said that the cable length "shouldn't" interfere on the particular matter, however he admitted that two possible cause could contribute:

1) A defective HDMI cable. Now, how can you claim a cable being defective when the picture is correctly displayed on the TV? Maybe some crosstalk interference?

2) The HDMI signals levels in one of the two HDMI interfaces (STB vs TV) not being 100% compliant. Again how can I prove that?

Some of you reported HD300s running really hot, maybe the HDMI interface of the HD300 is not 100% compliant or has some issues that are highlighted by using a very short cable, however even the other HD300 unit running with the 50cm cable was running hotter (or me being paranoid), so I replaced it with another 1mt long cable and again the unit seems running cooler...

What is your experience? The HD300 are now so rare particularly in Europe that one wish they will live forever...