However the cable that disconnected my 6800 XT, was the 6-pin riser power connector, not the usb-like riser data cable.
That shouldn't happen. Either it wasn't connected properly or it has a poorly soldered conector.
Yes, indeed the cable is not a standard 6-pin power cable, but is composed by 2 6-pin to sata male and female power cables.
So in the middle of the cable, there is a male sata connector, connected to a female sata one, that ends to the psu with another 6-pin male connector.
So, when i moved my rig to another location, the weak sata connector disconnected by mistake.