I have had a TX-SR604 for 3 years. It is excellent (when it functions properly). However, periodically,when I switch it on, the Zone 2 light illuminates, even though in the settings Zone 2 has been disabled. It takes several switching off- on cycles for the receiver to sort itself out and work normally. What could be causing it to show Zone 2 working when it is disabled? When zone 2 is illuninated, nothing, including the Standby works normally.