Strange Intermittent Audio Distortion Issue

I have encountered a strange and frustrating issue with distortion on Cross 1.7.1.
I use a Mac Mini running Lion (OS 10.7.2) and Cross 1.7.1. Output 1 is connected to an Onyx mixer. Ouput 2 feeds the internal audio channel on the Mac Mini. This configuration allows me to pre-cue the next song using the Mac Mini's internal audio chain while feeding on air audio through the Onyx.
Usually this works well. However, at times the cue audio coming from Cross Output 2 (Mac Mini audio chain) becomes distorted and unintelligible. It will clear up by itself after several minutes, but later on will become distorted again. Output 1 is unaffected and remains clear of distortion at all times.
At first I suspected an issue with the Mac Mini's audio output, so I re-routed the audio via the USB out and a Berringer U-Control USB audio adapter. I had the same issue.
Recently I've discovered that when the Mac Mini's internal chain audio becomes distorted in Cross, it remains clear on the very same audio chain from other audio applications. For example, I can play a cut clear of distortion from iTunes through the same Mac Mini audio chain while the Cross output remains distorted.
I'd like to be rid of this issue, so any suggestions would be most welcome.
Thanks,
Jeff
I use a Mac Mini running Lion (OS 10.7.2) and Cross 1.7.1. Output 1 is connected to an Onyx mixer. Ouput 2 feeds the internal audio channel on the Mac Mini. This configuration allows me to pre-cue the next song using the Mac Mini's internal audio chain while feeding on air audio through the Onyx.
Usually this works well. However, at times the cue audio coming from Cross Output 2 (Mac Mini audio chain) becomes distorted and unintelligible. It will clear up by itself after several minutes, but later on will become distorted again. Output 1 is unaffected and remains clear of distortion at all times.
At first I suspected an issue with the Mac Mini's audio output, so I re-routed the audio via the USB out and a Berringer U-Control USB audio adapter. I had the same issue.
Recently I've discovered that when the Mac Mini's internal chain audio becomes distorted in Cross, it remains clear on the very same audio chain from other audio applications. For example, I can play a cut clear of distortion from iTunes through the same Mac Mini audio chain while the Cross output remains distorted.
I'd like to be rid of this issue, so any suggestions would be most welcome.
Thanks,
Jeff