I thought maybe I had some pops in some sound splices of samples... maybe i forgot to shorten and fade them... but when i zoomed in and listened in different players, the clicks are in different places... WTF????  No clipping or funny peaks that I could see.
anyone ever see that before?

Normally, dropouts aren't a problem with exports, but they can happen.
 
Most often, it'll be a sampler or sample-based synth that's the problem. Or more accurately, a disk I/O problem. If you can identify one track that's the source of the pops, and it's a virtual instrument, you can avoid the problem by freezing that track before exporting. It might require a slow bounce.
 
If that advice doesn't apply, it's also possible that excessive DPC latency is causing the dropouts. A slow bounce will usually get around that problem. Just un-check the "fast bounce" option in the Export Audio dialog.
 
Another possibility is you're running out of RAM during the export. Easiest workaround for that is to disable the "64-bit Engine" option in the Export dialog. It won't audibly affect your export quality, but it will cut the amount of memory needed in half.
 
 

but it's in the rendered .wav, flac, mp3 playback in different places??? played back in audacity, WMP, whatever... the noise is still not in the same place on the recording.  must be halloween.

Still not clear. Are you saying a rendered wave file plays back with clicks and pops in different places depending on what player application you are using? That is completely different from the issue that a wave a FLAC and an MP3 rendering of the same project have a different location for the artefact. The latter is not unexpected since the processing of the same data by different algorithms will produce different output, including clipping at different locations. Or are you saying that the same project rendered twice as two different wave files causes the two files to have artefacts at different locations? Again not unexpected as random parameters in softsynths and effects actually produce different wave files on two different runs of rendering.
 
And if you have "zoomed in" on the "clicks and pops" what is causing the clicks and pops when you look at the file "zoomed in?"

The Interweb is the main culprit for me.  Most of the time it doesn't cause problems but pops and clicks always seem to happen during a great take  so I turn it off most of the time. 

Are you saying a rendered wave file plays back with clicks and pops in different places depending on what player application you are using?
even playing back using the same player to try to isolate the pops, it doesn't happen twice in a row!
 
And if you have "zoomed in" on the "clicks and pops" what is causing the clicks and pops when you look at the file "zoomed in?"
I've zoomed in and looked for a pop in the waveform but i see nothing... and when i isolate a pop area to look at the waveform, it won't be audible on replay, so I listen to that area over and over, and it is audible in a different location of the waveform, and of course, no pops visible. It doesn't even happen on other songs.
 
here's a 13 sec clip on sc... if you don't hear it then it's some type of interference from my system.  I listen to this and sometimes it's perfectly clean, other times i can hear maybe up to 4 pops or clicks...
 
https://soundcloud.com/markrelford/pop-check

I didn't hear any clicks/pops in the playback.
 
I've had a few occasions of rendering noise into my final file.  I've found the problems as bitflipper suggests - overtaxing the memory.  I've gone to always turning off fast-bounce for any larger project, and freezing any synth's before final rendering.  Once I had forgotten to bounce a Melodyne edited clip and that was causing it.  A few times it's been some of my more memory-intense plug-ins (such as convolution reverb), bouncing those tracks before rendering solved it.

if nobody hears any clicks or pops, then my system playback is introducing them.  But from what?
 
and again, it is not anything in the recording from a bounce or the buffer or fast-bounce... if I loop the playback, clicks and pops occurs in random locations at random playback intervals... it may play back 3 times clean, then a pop at 6 secs on the next playback, then a click at 2 secs into it on the next.
 
driving me nuts...
 
UPDATE  I just changed the Firewire driver latency on my Saffire Pro 24 to 'very long'.  I looped the clip about 20 times and only heard about 1 faint click on them all.  I was not aware that the setting affected normal computer playback.   After going back in to the mix control  to check it, the 'Firewire Driver Latency' was grayed out in Settings.   Maybe I'll call Focusrite and ask about this.

I have seen this before and in my case was introduced by Windows processes with higher priority. The wi-fi driver is a huge offender, but there are others. Take a good look at processes running and disable (esp at start up) ones that you do not need.

You might try listening to the rendered file on any other available system. It appears from the
responses so far the problem may be specific to your PC setup. The last BIOS for a Z77 is dated
January 2014, so your setup was tested only through Windows 7/8. You may need to update
your mobo or drop back to W7.