With the limited info I have I would guess either a cheapskate manufacturer that tried to pass the wrong gauge of cable as the correct one or a crappy connection between a plug and the cable.
I have one of these cables and after having analysed it, we (the guys on the forum and I :-)) think its more an issue of "dirty" plastics. If they get, e.g. carbon in the plastics used for injection molding the plug, it will conduct a small current, which will lead to heat, which will lead to charring, which will lead to more conduction, and you have a vicious circle going. So just to be clear, it's the "Mickey Mouse" plug that plugs in to the PSU that's faulty, not the PSU as such.
In my own case, the cable finally conducted enough to trip the RDC on my house, and that's when I started investigating. Having confirmed the problem, I then remembered the time on the airplane across the Atlantic when my socket wouldn't stay on, or the time on the train when the whole side of my car kept switching off... I had inadvertently travelled the world, leaving darkness and despair in my wake...
Pictures of my measurements (and discussion, in Swedish I'm afraid). At 20mA, the cable developed 4.6W and my measured 80C (176F) is reasonable. I didn't really notice it before, since the powersupply gets quite warm as it is.