Adding the command-line ways to enable this property at the server level :
i) using 'AppCmd':
%windir%\system32\inetsrv\appcmd.exe set config -section:asp /scriptErrorSentToBrowser:true
ii) using 'adsutil.vbs':
%SystemDrive%\inetpub\AdminScripts\adsutil.vbs set w3svc/AspScriptErrorSentToBrowser true
Jason, do you mean the same ASP page (with error) in the subdirectories and root folder, but only the one in subdirectories showing this general error message?
Anyway, try the above way to see if you still have the same problem.
Ray