I just got an i7 SP4 and am having an odd issue. If I have the power adapter connected to the SP4, remove it, and then try to turn the device on it will just sit at a black screen. The keyboard lights come on, but it won't wake up - I have to hold the power button for 30 seconds to reboot it. The same thing happens if the screen is off and I connect power. I've had it happen after a long wait, when it's in hibernate, and also after just a few minutes (before hibernate kicks in). If I turn the screen on prior to removing or attaching the power adapter it works fine. Has anyone else had this issue? Is there a known fix? I haven't been able to find anything online.