If you post the make and model of the machine in question I can guide you straight to it. You could also try this. Open the control panel, look under hardware for Device manager, in Device manager look for the Wifi component. Right click on it and choose properties, look across the top for Driver click that and then roll back driver. Your driver may have been updated? This will return it to the previous version but in any case post the make and model as I wrote above..