The CL is maybe not intended to be used on trax but rather the master or busses I understand?
However I have used it subtly on my vox and guitar trax and love what it does but it often goes dead. 
Just quits working. It's part of a preset I saved in Pro Channel.
Anyone else have that happen?

I recall other reports of the same problem in X1.

Ah! thanks. Fixed in X2 I presume?

I do not recall reports of it happening X2 and have not used Concrete Limiter much since buying Pro-L

I haven't seen this happening in X2a, and I use it on any tracks that need it.

It has happened to me once in X2a, just the other day.
 
I removed it and re-inserted it, and all was fine.

I had the same problem, one or two times.
I think it was when i have saved a PC preset including the CL (so i don't do it anymore).

This happened to me just yesterday on a bus in X2a.

I tried absolutely everything I could think of to try and get it to spark into life - remove module + re-add module; close + restart SONAR; I even rebooted my PC to no avail.

In the end, I had to create a brand new bus and repopulate it with the VSTs and Pro-Channel modules and settings.

It's happened quite a few times since I got the Concrete Limiter, but I thought it must have been user error on my part. At least I know that others have had this happen.

It would be nice if it could be determined when this happens and whether it's the CL's fault or not. It sounds pretty serious to me if some of you avoid using it in certain situations.

Maybe they don't know?
Has anyone told them?