A speaker button keeps turning the speakers off & on & B doesn't work at all.

Swap wires between speakers and to make sure it is not the amp, the head unit or wiring. If the right speaker still doesn't work touch a 9v battery to the speaker terminals for a second to verify if the speaker is good or bad (a pop the speaker is working nothing the speaker is bad)replace. Otherwise check the wiring between the amp and the head unit. If all the wiring is good you may have a bad channel in your amp(bad internal connection or bad component(s)) or last there could be a bad channel output on your head unit. If that is your only right speaker and you don't have one in the door and you use an ipod as a source check the cord!

I had the exact same issue with my AVR-391 and tried resetting per user manual but did not help.
I unplugged all speaker wires from both ends (I only had two), made sure they weren't damaged and/or had loose strands that could have been touching the other terminals or anything else then connected them back. I also cleared the receiver of all stuff that was sitting on top of it (pic frames, remotes etc). Turned it back on and problem has not come back. That was a month ago.

Assuming you have checked the obvious mute button, all aftermarket decks have a ground fault system integrated. If one of the leads to the speaker wires is touching ground, then it will shut off all outputs to the speakers. This is easily checked with a volt meter or a speaker itself, whichever is more readily available. Disconnect all wiring for the speakers you just hooked up and simply hook up only one speaker to any of the sound outputs. Do not let the other leads touch anything. Turn on the radio and if it works, you need to chase a speaker wire that is touching ground, plug in one at a time and go from there.

The speaker either may not be wired properly make sure that you have taped off the speaker wires individually (where they were cut) otherwise it will short out the signal preventing the speaker from working if they touch anything (even each other). The offset is caused by improper power readings coming from what ever you had plugged it in to house outlets give off different readings than a normal car battery would. If it still doesn't work you may have to replace it. you should contact your vehicle manufacture for more info on how to do that.

You should double check your connection to the sub. Make sure that no speaker wires are touching each other. Sometimes you won't get anything to work if pieces of the frayed bare wire on the positive cable are touching parts of the negative.
Is this a dual or single voice coil speaker? or to re-phrase it, does it have one or two speaker terminals?
I would also check your line in to the amp. Make sure it is sending a signal to the amp. If available connect the audio signal to some other component like a boombox or AV Receiver that has a proper connection.

Sounds simple... usually "protection" means that a speaker or a speaker wire is shorted out. Or that the volume is just too damned high... how loud is the receiver's volume setting? If the bass tone control is jacked and the loudness button is on, even with no shorted wires, the amp can go into protection from an internal overdrive. Might be that you just need to do like your mom says and turn it down!
If you have an ohmmeter, speaker or wiring problems are easy to test, if you don't, you can still do it all mechanically... here's how
Turn off the receiver and start by disconnecting your speaker wires at the back of the receiver. With all of the speaker wires removed, does the thing still go into protection when you turn it back on?
If not, good. If it does, find a service center.
Re-connect the speakers to the appropriate terminals one speaker at a time, turning off the receiver each time you make a connection. After connecting one speaker, turn the receiver on and see if it shuts down. If not, then turn it off and add one more speaker.
Do this until you find the culprit. Leave that suspected bad speaker's wires disconnected from the receiver and test all the rest, connecting all but the bad wires.
Now, disconnect the speaker from the other end of the bad wires and spread the bare wires apart so they don't short out. Connect the wires ONLY at the amplifier end and turn the amp back on. Protection?
If yes, the wire is shorted out somewhere. got cats?? If everything is OK, turn off the receiver and reconnect the speaker and test again. Make sure the wires aren't shorted at the back of the speaker. You really need to check all the speakers to make sure their connections are "clean" and make sure that there are no stray wire strands anywhere or that the wires aren't stripped too much so they might be able to short out. After the wires are connected to either a speaker or an amplifier, you shouldn't be able top see much of any bare wire, but you already know that, right?
Some folks strip way too much off the wire and the wires simply touch the wrong things and ... badness happens.
If all the connections are clean and the receiver still shuts down when this speaker is connected and the receiver is turned on, swap a working speaker onto these wires, leaving the suspect speaker disconnected and making sure the other bare wires won't touch anything or each other.
Back on with the working speaker... good? If so, then we're determining that the problem is probably in that one speaker. If not, then we have a deeper problem.
Reconnect the suspect speaker to the other wires and try again. Good? Then you have "fixed" the problem by cleaning up the wiring connections. If it shuts down again, then you need to fix or replace the bad speaker.
If everything works now with the volume down and such, then just use a little self control. If it's still messed up, you may need a trip to the service shop
Good Luck

The cables from the amp to the speakers could be shorting out, the speaker(s) could be shorting or going bad. The impedance of the speakers could be to low for the amplifier. The amp could be overheating because of any of the above. Turn the power off and try disconnecting one speaker, make sure no bare wires are touching. Reapply the power and observe. If it still does it , reconnect the speaker and preform same test to the other channel. The previous test can determine the side that has the problem. If the problem is still present the speakers and cables need to be checked with an ohm meter. If the cables and speakers check out then the amp speaker outputs need to be checked to see if there is any DC voltage present. If DC voltage is present on the outputs then the amp output section needs to be repaired.

Speakers wire conductors should not touch anything but the points on the amp and one speaker terminal each. Look again.

Try Doing Grounding The Mute Cable To Somethign Else And MAke Sure Its Not Touching Anything And Make Sure Your Soeaker Wires Arnt Touching Each other

does it keep cutting in and out?
if so i think you have your polarities crossed
make sure you have negative to negative positive to positive