Steps to recreate:
[LIST=1]
[*]File->New
[*]Etc->Clear Quest Filepath and click "Yes" (bug still happens even if you skip this step)
[*]Etc->Options->Settings->Auto-save Interval: 1 Minute
[*]Wait 1 minute
[*]Observe Saving Quest msgbox briefly appears
[*]Observe "Untitled Quest" still appears in ZC Editor title bar
[/LIST]
It appears to have not actually saved, because shouldn't the editor pick a filename?