Problems mixing and editing audio

Over the last week I've been doing a bunch of mixing of some demo recordings my band has recorded. I seem to have run into an issue that occurs fairly often when I make some edits – say, for example, I cut a note out of a bass part and then nudge it a hair to the left or right – and then I try to hear it, and there's an audible click, the master bus meter lights get all maxed, and nothing is audible. I can continue and do some things like save the project, or undo the move... the play cursor moves like it should, but I can't hear anything other than occasional random clicks. If I shut down SONAR and restart it, I can continue... but it's not long before it happens again. It's extremely difficult to mix this way! 
I have several plugins running on the vocal and guitar and bass tracks, including the RED 3 compressor and RED 2 EQ, the Softube TSAR-1R reverb, and Drawmer S73 Intelligent Master Processor is on the master bus. I suppose I might just be taxing the system too much. Some things I tried that seemed to help: deleting some tracks that weren't worth keeping; updating to the latest driver for my interface... 
Anyway, I know there are a fair number of users of my interface – Focusrite Scarlett 6i6 – and was wondering if anyone else has been encountering such issues. My system specs are in my signature... it's a fairly beefy system.
Thanks in advance for any suggestions you might make...

I would suggest, instead of cutting out a note and nudging it, set the track Edit Filter to show transients and nudge that instead.

Being an owner of a 6i6 that will not be the problem. It is a solid interface with stable drivers I'm using 1.8. 
 
Make sure you check the zero crossing thingy in preferences. 
You sound like your cutting and pasting during a "non" zero crossing so you will get a click if that happens. 
There are a few ways to avoid this,  one mentioned above. 
Another is to split it out leaving lots of head and tail but avoid the other notes,  and copy, and paste to a new lane where you can move it and adjust the crossing points. 
I also sometimes just copy the same note from somewhere else in the song and paste that overtop and adjust the overlap. 

how is your ripple edit set
sometimes i forget to turn it off

AlChuck
nothing is audible

 
I can also agree with the zero crossings as a better method of working but to suggest this would make sonar lose audio ? I don't think so.
I could see it making an audible clipping noise but nothing that would blow the roof off and lose audio.
 
It sounds more like a downstream FX, overloading because of clipping hard enough to drop the audio engine.