I've also installed WengoPhone and it has the same mic problem. I can't get a normal mic, to test, 'coz i'm in Turkey right now, so I've got booze, **** and linux-mint. I have Mint as a second system, installed 6 month ago. My main system was WinXPsp2 (never paid a cent), and everything run smooth, until, the first day in the Hotel (Concord, by the way) my primary ntfs partition got pwned by some nasty fragmentation, or a virus, hell knows. I was lucky enough (thanks to all mint staff for this) to discover the fixntfs routine, so that I could resurrect my second ntfs partition, with all the music, work, and p*rn ())).
But, enough with the off topic. I tried to play with alsamixer, after the problem occurred, but no luck. Perhaps someone could advice some other linux command to try.
I suck at basic electronics, but if you are right, it means I'll have to "unscrew" my laptop, to see, if everything is intact inside, or isn't it?