I installed Classifieds on a pristine WP 3.1.1 / Buddypress 1.8.1 installation. It didn't work just generated 404's / fatal errors when trying to access anything to do with classified, although the remainder of the site still worked OK.
I deactivated the Classifieds plugin thinking I'd be back to where I was before but it has seriously screwed up the site with MySQL warnings throughout the site.
Reactivating the Classifieds plugin removes the MySQL warnings but I've then still got the 404s / fatal errors etc when trying to access anything to do with the Classifieds plugin.
I've reinstalled WP 3.1.1 - but still got all the MySQL warnings.
I've reinstalled the Theme (not one of your theme's but it was working perfectly until I installed the Classifieds plugin) - still got all the MySQL errors.
The only thing I've not done yet is to physically delete the plugin via ftp but I suspect that this will not resolve the problems that the plugin has created. I don't see why deactivating shouldn't work - like it does with other plugins?
Question - how do I get rid of the Classifieds plugin and get the site back to how it was beforehand?