Two fairly new W7 laptops which were working fine all of a sudden don't connect to each other or to themselves over a wireless network (a workgroup). Both can connect to other Win XP machines. But neither W7 laptops are visible to, nor can be accessed from the Win XP machines. File & Print sharing won't stay turned on no matter how many times I try. Can't change computer description or workgroup in Advanced System settings (i.e., grayed out completely). Internet works fine on each. Tried setting up homegroup - still no change. Tried System restore - no luck. Using W7 Home Premium on both laptops. Any ideas?