I recorded a bunch of vocals for my project, they span 3-4 tracks and about a dozen take lanes each. I used Melodyne on some of them. I am now tweaking the details (getting syllables lined up, normalizing levels, all that) and somehow now have a phantom vocal track playing that I can't find.  
 
So I've muted every track in the project, including hidden tracks. I've bypassed all audio effects. This phantom audio is still playing. The audio tracks all output to a bus used for vocals. The only way to make the phantom audio go away is to mute the bus itself. 
 
How do I find the source of the phantom audio?

Are you sure you don't have a hidden track? Look here. 
 

As mentioned in my post, "So I've muted every track in the project, including hidden tracks."

a clip over another clip maybe?

Are you using Aux Tracks by any chance? just curious cus I sometimes get audio bleed when using Aux tracks, mainly as buses. Similar thread here http://forum.cakewalk.com...n-Tracks-m3687247.aspx to which I replied a little while ago.  

In Dim Solo mode ?

 
 
Or in Exclusive solo mode ?