Hey Guys,
Thanks for listening. Yes, I checked all tracks and master bus for clipping. I have a brick wall in the last position of the master bus as well. I'm actually doing very little Limiting on this song on the master bus; I am probably only lowering by 1.5 overall.
What has happened to me once before while using X3 is that I have suddenly had a stay track going direct out to the interface and by passing the master bus. I couldn't figure out on that occasion how it had happened. I didn't look for that on my final bounce, but will later this evening when I get home.
Edit: checked all tracks and busses, no clipping. When I started turning off FX's one by one, I discovered the problem. I had added Waves R Bass to the bass track and for some reason, it seems to mess with other tracks as well. I created a nice bass tone, but some how is leaking onto the main vocal track and distorting that. I am going to work on this with fresh ears in the morning.