hmm..do either of you have another laptop or wifi device you can duplicate this error with? it might be a router problem? if that's the case, then any amount of tinkering with your mini9s wont solve it, regardless of the os.
cuz if it connects, then it works and it shouldnt be a hardware problem. unless it's heat related..then you might wanna try a cooling pad. but other than heat, i really dont see why it would connect..and then, without rigorous shaking, would disconnect. something's gotta be telling it to disconnect. maybe check your bios (dunno if there's any wifi options in there tho..but that's the only other constant that's present in all 3 os installations)..