iFolder refuses to sync because of "deleted folder"

iFolder 2.1.7 running on NetWare 6.5.6. One user says his iFolder
hasn't synced "in months." He gets an error "Unable to synchronize
because your iFolder S has been deleted or removed."

I had him uninstall and reinstall the iFolder client. I also tried
removing his iFolder data from the server. He still gets the same error.

Should I try having him exit the iFolder client, then delete C:\Program
Files\Novell\iFolder\<user ID> and restart? Or might that cause even
more problems?

Thanks