Is it possible, that there are some old tables left in your joomla database? If so, you should uninstall component, manually drop tables named yourprefix_grids and yourprefix_grid_conn, and than install your component again. Or contact us by e-mail, because I have just prepared a package that does it all.
About database driver error: make sure your oracle and mssql drivers were installed to libraries/database/database/, and second: you should write for database type 'oracle', 'mssql' or 'mysql' or 'mysqli' and nothing else. But this is rather connected to the first problem if my guess is correct.
