It was a wake from sleep. 13 page PDF contract (800KB). It was the only app open. There really was no real reason for a total freeze requiring hard power off.
And yes, you're right. Only took about 15-20 seconds to reboot.
For me; this was the only time it's frozen. That being said...my Lenovo W520 with Windows 7 has only frozen 2 or 3 times in the nearly 3 years I've had it.
I simply had Adobe Reader open (Metro UI). I was just going through a 15 page contract / PDF (client had their own copies to follow along so I didn't need to project onto a screen). All apps were closed.
It's Windows; it happens. Just annoying.
So when I wake from sleep, the 10-15 seconds of "limited" seems to be a delay in the WiFi realizing the SP3 is awake and that it should search for WiFi. It self-resolves, but also doesn't happen on 2.4
So basically, when coming out of sleep, my SP2 will be in Limited Connectivity mode for about 30 seconds, but automatically recover itself.
Connection is typically 250-300Mbps with my router.