In Logic 8.0.2, if I send an audio track to an Aux with CMX inserted and the send is at a level higher than -infinity after the last region, Logic overloads on two cores of my 8-core MacPro, stops playback and gives me the System Overload error message. If the send is set to -infinity before the last region ends, the error doesn’t occur. 
Sorry for the delayed response! This sounds like a denormalization bug, though it’s odd it only occurs in Logic. I will look into this today.
Bleen, are you sending only one track to the CMX aux? Does the overload depend on specific audio on the source track, or does it overload with any audio (or no audio)? Thanks.
Yes, I was only sending a bass track to it. Although, and this may be helpful to you, it was coming from another Aux track. I have two audio tracks (DI & amp) bussed to the bass Aux and then the send to the CMX Aux is on the bass Aux.
I think this problem is audio signal dependent. Any chance that you could send me (a piece of) the specific source audio that triggered the problem? Schwa at stillwellaudio dot com.