Audio system problem

[Structureboy]

To Anyone who might have an idea how to solve this problem...
I was replacing my 9006 headlight bulbs (55W) with some PIAAs (51W). Playing it safe, I disconnected the negative terminal from my battery while installing the light bulb.Afterwards, having reconnected the negative terminal to the battery, I started up my car and tried to play a CD, but it wouldn't play. My factory DD receiver won't switch to either radio,cd, or cassette player. It seems like everything else in the car was not affected by my disconnecting the negative terminal, just the receiver seems to be faulted. I don't think it's because the receiver has no power, as it still lights up (like the theft-deter "SEC" light is still on...however doesn't go away) and the tray still accepts CDs. Anyone who might know what the problem is, any help is appreciated. Thanks in advance.

[Slushangar]

I believe your radio "thinks" it has been stolen since the power was disconnected. It has made itself useless until the security code has been entered. You need the enter the security number for your radio. (3-digits I believe) I hope this helps.

[Structureboy]

thanks for the help slush, actually it was a pretty minor problem in the end. my receiver, you were right, I believe it did think it was stolen, so all i had to do was research the owner's manual again and enter the security code for the receiver-and it works fine now.