"Random" mix bus distortion issue

[globaleric]

Here's a weird one which drove me crazy for an hour last night:

While mixing a song, I've noticed a short distortion (about half a second) happening just once during one syllable of a chorus which is played/sung 5 times in total. Ok, so let's check for the obvious:

- soloed every track - each track sounds fine alone, so it's not on a track
- no channel, bus or master fader is overloading. The peaks are around max. -5dB during that syllable. There are higher peaks elsewhere in the song.
- checked and disabled all plugins - distortion still here, no overloads
- lowered the volume of all channel faders by 3dB... distortion still here, sounds exactly the same as before, just 3dB lower in volume *argh*
- started soloing combinations of tracks and bingo - it's the combination of the two lead vocalists!

Again, each vocalist soloed sounds fine, and the same syllable appears several times elsewhere in the song sounding fine with very similar gain. So I basically could copy & paste that syllable from the previous chorus. However I've ended up with a volume automation of the less audible vocalist in that part: A short -4dB dip did the trick, the correction is not audible in the mix.

But still - what happened here? Is this some random "nagware" feature of PT LE telling me "Buy a HD rig?"

[globaleric]

bump...