no sound on speakers after using headphones

I'm hoping someone can help me out, and that this is something really simple. I just got my first PSP. Everything worked fine at first, but now there's a problem. Although I had sound from the speaker before I plugged in headphones, now I can't get any. I still have sound perfectly through the phones though (when I plug them back in). I've tried cycling through the sound styles (pressing the musical note button), checked sound settings, even reset system settings, but nothing. I, of course, have the headphones all the way out and I get complete silence. Is there another mute, or a setting to shut off internal speaker that I don't know about? Any help would be appreciated.