ViperAlley isn't a demo, its my own website that uses Classifieds. I'll check into the issue you discussed, but since its a modded Classifieds, the problem is more likely my own. (Note: I fixed the problem on viepralley with that page).
I can't speak for the sites you are talking about since I dont know what they are, but we have many sites using Classifieds without any problems.
Please do not PM me for support or sales questions. Thank you for your understanding.