Originally Posted by sirmaru
If the second one does the same, then I will conclude its a firmware problem.
I have no idea how you'd conclude a firmware update fix would something which is caused by the Kindle being shaken. Nothing in the Kindle 3 cares about orientation as it doesn't have the accelerometer that the DX has so it doesn't even know what orientation it is in.
If shaking your Kindle causes it to reset then it is a hardware issue. If it happens again then you're just unlucky and got another bad Kindle as a replacement. Somebody on this forum is apparently on their 3rd Kindle already because they're really unlucky and keep getting bad ones.