Hi Phil,
Yours is the first report of this behavior on OS X. There is a very comprehensive crash report that OS X generates that would be very helpful.
When the application crashes, please launch /Applications/Utilities/Console.app and then open the "User Diagnostic Reports" item. You can drag the most recent Audition crash report listed there as an email attachment and send it to audbugs@adobe.com I'll make sure it is shared with the developers and added to the bug report. (It may also give us some more immediate guidance on what's happening.)
Thanks.