Well come on Mixture, the Win 8 spurt! Help the poor fella out here!
You rang, Sir ?
I've been mulling over this one a little, off the top of my head it sound like one of those instances where Windows gets itself confused over what network you're on and puts you on unassigned (or whatever it's called) and cuts you off from the internet. Fixable but a pain and the range of fixes vary.
But I've also been a bit busy and haven't had a chance to play with 8.1 much, although it is on my to-do list.