UPDATE: Anyone having the same problem as above.. there is no way you would be able to resolve it.. there is obviously a serious bug in the ranking calculation starting with version 2.3.0
As far as I'm concerned.. if you didn't keep a database backup from version 2.2.5 then you're probably stuck until the author resolves the problem and releases a new version..
Otherwise, if you kept a backup.. then do the following to resolve all your problems:
1) Download the old script version here http://downloads.wordpress.org/plugin/football-pool.2.2.5.zip
2) Unzip the folder on your local computer
3) Upload the folder to /public_html/yourwebsite.com/wp-content/plugins (overwriting version 2.3.x)
4) Go to PhpMyAdmin from your Cpanel and import the database you backed up before all the 2.3.x versions were released
Now you should be fine...