Right, assuming you haven't updated Vista in the past week, it's probably due to some sort of interference.
You might have better success at changing the wireless channel in the home hub from automatic to a number. It could be trial and error to get a good connection though, but I would start with channel 11 (there are 11 channels so work your way down). Chances are, someone in your block of flats is causing the interference.
How to do this