I think it is something wrong with your settings. You stored the documents which you want to sell under the root of your site ? You should put these documents somewhere (maybe in one folder under the root of your site or somewhere in your server).
Please do that and it should work well. Do you need my help to remove the .htacces file ?
That's strange. Unless you setup the Documents path to the root folder of your site, the issue won't happen. Could you please submit a support ticket sending me admin and FTP account of your site so that I can check and correct it for you?