In any normal circumstance the line in connector should *not* be used for an analog microphone...the signal produced from microphones is very low and must be amplified for it to be usable (and mic inputs usually undergo hardware amplification). Line in inputs are for sources that do not need amplification. If you use a line in input for a microphone you will likely have to use software amplification to boost the signal, which will result in worse quality than simply using the microphone input and setting it up ALSA correctly to use it.
Thanks, T3slider, but this is the only way I can get the damn thing to work. Don't think I didn't try the microphone in the microphone hole - it was the very first idea I had.
Sometimes if you've tried all the reasonable approaches, and then the silly ones, and things still don't work, you might as well try the lunatic ones.