Intermittent crackle during playback

[fathead]

Help! I am running MLCD 2.4 on a twin 500 G4 w/sytem 9.2.1 I've never had a problem before. Now suddenly there is what I assume is a clock error.An extremely odd crackly popping that happens throughout playback. It is very inconsistent. as soon as I stop playback it dissappears. Usually with a clock error, it will continue even when not playing a file. It's not behaving like a true clock error but it seems like one nonetheless. The strange thing is that Pro Tools will play any and all of the same files without a glitch. Digital Performer plays everything back perfectly as well. It's ONLY MLCD!!
I have an Aardsync word clock generator controlling everything in my studio so it is usually rock solid. I also have a video distribution amp to everything... al have professional shielded cables.
I have trashed preferences countless times. I have trashed the entire MLCD program and re-installed it. I have trashed the DIGI preferences. I have started with just a basic extension set and added ONLY the Digi extensions. Nothing works!
Anyone out there ever hear of such a thing? Any suggestions?

[sonicprod1]

are you set to internal sync on the setup window?

[fathead]

I've tried it all ways. Internal and digital. My studio is usually clocked perfectly. That is why it's so strange. Also, as I said, the files play perfectly in Pro Tools and Digital Performer. The click dissappears when playing back under Sound Manager and it does not burn the CD's with the click.

Weird...