Help please?, Head unit Problem Options

[Aleksa]

Hi i installed a Sony Xplod head unit on my 95 celica sx and now only my rear right hand side speaker works. I bought an adapter for the celica and for the Xplod and it clicks perfectly together. I hooked up the antanna too. When i first installed it none of the speakers worked and then a couple of hours later i turned on the car and the rear right hand side works. The head unit works fine though, all the settings, mp3 playing, etc works fine except for when i turn it on it says "failure" on the Xplod head unit but then it plays music and radio fine, except for it only plays it through the rear right speaker. I'm not good when it comes to electrical stuff, especially around a car, so i was hopeing to get some helpful insight from some of u guys? any ideas on why it isn't working? thanks....