Since you are receiving this error message, it is indicative that your description HTML contains a path to an image file that is located on your local system. Assuming the image is located on your C drive, you should be able to find the offending image path by searching your description HTML for "C:"
One you have removed any and all paths to locations on your local system from your description HTML, you should be able to successfully post your listings without encountering this error.
Any additional questions or concerns? Please contact our customer support department using the appropriate link on our help page: http://www.auctiva.com/free-auction-software-help/help.aspx