Oh! I know exactly what ur talkin about. Its called Reverse mode. Its basically a feature in Pioneer's OEL, as preludacris said...
To turn it off, hold the function button while the unit is off...then go to reverse and select OFF.

U probably turned it on accidently around the same time u were installing the neons. Functions like this can be turned on/off by pressing/holding the buttons 1-6 while the unit is off...

Good luck!