Following Steve's suggestion fixed my problems! (At least for now).
Many thanks, I've been trying all sorts of driver manipulations to get it to work.
One thing I noticed is that once the power savings kick in, the connection info would display 54Mbps even though my router is capable of 300Mbps (the adapter usually shows 80-117Mbps in the status window). To me, it looks like windows suspends the adapter partially (only the N part) then gets confused by that and can't wake it up - because it's not fully in sleep mode.