Privacy List Error. Can’t add volume to privacy

Hello,
I got this annoying error message while adding volumes to privacy now I can’t use Spotlight on Leopard at all. I searched for this error but could not find any result. I need your help to resolve this weird error message so that I can use it properly. Any help would be greatly appreciated. Thanks in advance.

Privacy List Error
The item couldn’t be added or removed because of an unknown error.
