Oh Crap! I was hoping this wasn't Froyo related. I just got my phone a few days back and of course when the froyo buzz hit, I just had to jump in. I had this very thing happen to me last evening and thought it was just due to mucking with different app installs and heavy usage but ended up having to reboot to get my earpeace/phone volume back as it did this very thing.
Now I'm really on the fence as to flash back to 2.1 and lose my setup but gain stability? Blah....