Ok, you know that warbling sound you get when you're tuning two strings to each other, and one slightly is out of tune? It's easier to hear if you pile on the distortion.

Anyway, for no discernible reason, the sixth string on my guitar makes that noise when I play it. Just the sixth string, muting all others- it "warbles". This is painfully clear if I play a harmonic at the fifth fret.

It might have something to do with the fact that I recently blocked the trem. Anybody ever seen this before?