When trying to save multitrack session this message comes up sometimes with a progress bar that never advances. After waiting several minutes, clicking the close box leads to "Audition not Responding" requiring a force-quit, causing session to not close properly. I don't see any mention of this dialog box anywhere on this support site - has anyone else ever seen it?
To all intents and purposes, that's a crash (believe it or not!), so you need to follow the steps here: Audition crashed - now what? and post the text of the crash log into this thread initially, because it might be obvious as to the cause. If it isn't, then you can submit it to email@example.com - but in general it's best to post it here first.