Weird reverb tail at beginning of song...

As some of you know I've been using Sony Vegas Pro for my audio work for quite some time now.  I use volume envelopes extensively for mixing.  I just did my first full mix with Sonar X1 and I'm getting this strange reverb tail before the song even starts.
 
Here's the way I have my mix set up.  I always allow about 1/2 second from the start time of the mix to the actual first sound of the song.  This is a habit I picked up a long time ago so that CD players will be sure to catch the first of the song when it starts playing (when starting the CD or switching CD tracks).
 
Now, using volume envelopes I have each track muted up until it's actual sound starts.  So you should not hear anything until the actual track info starts playing.  BUT...when I start playing the song, I hear a distinct reverb tail during the 1/2 second before the song starts...even though all the tracks are muted with the volume envelopes.
 
Is there some sort of "look ahead" feature that I'm not aware of?  I just can't comprehend why this reverb tail is audible when the song hasn't even started yet.  Any ideas???

I just thought of something as a work-around.  The reverb tail is actually coming from my acoustic guitars that I have bused to a sub group.  I have the reverb placed in that bus.

So, I put a volume envelope on the bus itself and muted it until the guitars start.

That cures the problem...but still doesn't explain why I was getting the reverb tail to begin with.  If the tracks are muted right up until they start playing...why would the reverb be audible before they start?

No worries mate!

Thanks sven...I'll give that a try also.

I do that routinely Kalle when I'm nearing the end of a project.

Of course, you can't go slip editing clips this way in any other place than at the end of your project, so unless you've unchecked "Play Fx Tails" and you stop your project anywhere else in the timeline, the next time you press the spacebar, the buffered tails will be heard.