There is another way that does not involve having to delete all your banned IP addresses.
Edit the file wp-ban.php
At line 200 you will see
echo $banned_message;
exit();
change this to
echo $banned_message;
return;
exit();
Save the wp-ban.php
Go to the BAN admin menu and take out your own IP address.
Then edit the code back to read:
echo $banned_message;
exit();
Save the wp-ban.php