I have a APC UPS plugged into my iMac, all works fine. But it doesn't seem to be keeping the settings. I have it set to turn off display after 8 minutes, and have turned OFF dim display before going in to standby. But no matter if its selected off or on, the display dims. I tried unplugging the USB cable from the APC, it still dims with the feature turned off. Whats the deal?