If you are obtaining this error message upon listing download it means the Zetsy has reached some limits as set by Etsy (It is NOT a program error). The error is sporadic because of this - meaning Zetsy operations may be fine in the next hour. We're hoping to get this problem resolved as soon as possible. See http://www.etsy.com/developers/discussion for some details.
Good New/Bad News. Once again we are exceeding our limits tonight. We have asked for a further increase from Etsy. Sorry for any issues this may be causing.