You would have to search your database and remove all instances of the installation.. You can do this in phpmyadmin, but if you don't know what you are doing you can hose your database.. Not recommended.
when you uninstalled the mod, how exactly did you do it?
You should go find the modification and read the installation file and then undo everything your were supposed to do to install it. It could be that you just left a couple of files still uploaded on your site and that is what is causing the database problems.