Comment 36 for bug 484856

Paul, that was very illuminating. Mainly, because the same symptom occurred to each machine, and (I am assuming) that they have different hardware, then this is probably not a driver issue. Most likely, this is a configuration issue.

Examine the settings you have for your Windows machines and see how they compare to the wireless settings (wlan0) of your laptop. See how they differ (assuming that they are both automatically set). It is possible that network-manager is not properly auto-configuring anymore.