My K3 works just fine without the cover. What I've been doing, successfully, is to turn the K3 off, using the power switch until the screen is blank, then and only then, install my unlighted case. With the power off, turning the K3 back on takes about as long as a normal power-up from sleep mode, but only after removing it from the case.
On my K3, when it froze up prior to recognizing the cover problem, I plugged it into the 110V wall outlet until it was completely recharged (green LED at the switch). It then functioned normally and has ever since.
There is either a contact problem with internal wiring (mentioned elsewhere) or the possibility that the hard case presses on one or more keys which sends a repeated keypress signal to the CPU (even in sleep mode) which locks up the CPU.
Turn the K3 OFF, then use the cover. Remove the K3 from the cover, then turn it on. This should get you by until the cover problem is solved.
