We have an APC 650, as a power source for a server, and it has been working several years without a problem. Then recently it sometimes shuts down the server. The overload light went on today, yet there is nothing else except the server plugged into it. The monitor is plugged in another oulet. However there is an air conditioner plugged in a nearby outlet. We're wondering if that may lower the line voltage and cause the UPS overload light to go on?