Help, my iBook's mic stopped working! What to do?

[the Falcon]

When I wanted to use the microphone in my iBook G4 (Tiger) today to tune my acoustic guitar with GarageBand, it didn't seem to pick up any sound at all. I first wondered if it was a problem with GarageBand, but when I try the microphone in Sound preferences, it doesn't pick up any signal either. I tried restarting my computer to see if it would go away, but that didn't work either. It's really weird, cuz yesterday the microphone still worked and I was very easily able to tune my acoustic guitar in Garageband. The only thing I did on my iBook between then and now is play THPS4 with headphones on, so I don't think I blew up the mic or anything like that. I really don't get it. My System Profiler says:
Internal Microphone:
Controls: Left, Right
Playthrough: No
PluginID: TAS
Is that all OK? I have no idea what it means or if it's even related to my problem, but thought I would just mention it, just in case.
If anyone can help me out here, I would be ever so grateful! I really need to be able to use the microphone in order to record music and do voice chat. So, if anyone of you knows how I can fix this, I would really love to hear about it. Thanks in advance for your help.

 

[840quadra]

What is the gain currently set at, and is the input set for Microphone as opposed to something else.

In Garageband, do you have "Monitor" turned on ?

 

[the Falcon]

What is the gain currently set at, and is the input set for Microphone as opposed to something else.

In Garageband, do you have "Monitor" turned on?

Input volume in Sound preferences is set at 50%. Setting it lower or higher doesn't make any difference: the Input level shows 0 at all times. "Choose a device for sound input" is set to Internal Microphone/Built-in (Name/Port).

I don't think it matters whether I have "Monitor" on or not, as I'm not trying to record anything; I'm merely using the tuner. However, I just tried recording a voice track with Monitor on, and it records and plays back absolutely nothing—not even static. Playback (of songs I recorded earlier, for example), by the way, works just fine;I just can't record anything. This really seems to be a microphone problem to me.

I hope this makes the problem any more clear. It sure isn't to me.
I just hope my microphone just didn't spontaneously die or something—which would be quite surprising to me, since I treat my iBook with the utmost care. I sure hope the hardware didn't just blow itself up or something. *knock on wood*

 

[istonedu321]

are you headphones still plugged in. if so try unplugging them(just the idea)

 

[the Falcon]

are you headphones still plugged in. if so try unplugging them(just the idea)

Thanks, but no, they are not still plugged in.

And my microphone is still not working.