If you've been getting this message when you start an Audition session, it appears to be down to an issue with the CC app itself. That's being worked on, but you can resolve the issue quickly and easily by following the instructions that _durin_ posted. He said:
"Hi everyone,
We've investigated this and it appears a recent update to the Files Sync functionality in the Creative Cloud desktop application introduced this problem. It's not a Windows issue, but has to do with how Audition tests if it can write to a directory (by creating, then deleting, a temporary file) and how quickly Creative Cloud Sync locks files for backup.
We're working with the CC team for a solution as quickly as possible. In the meantime, if you launch Audition without opening a session, and follow Roger's suggestion to change your Auto-Save Backup Location to anywhere but the Creative Cloud Files folder, or disable File Sync in the Creative Cloud Desktop application, you should avoid the problem until a fix has been made available."
Hopefully this will be resolved soon, but just changing your backup location will get everything functioning again.