The only possible help I can give is: Go to Tools, then Options, then Filters, then Keywords. Type in the name of the episodes that you don't want to get, and then Limewire will block those episodes from coming up as search results. Hopefully then the only episodes that will come up are ones you don't have. If you find a new episode then add it to the Keyword list and then Limewire will not just show that episode again.

If that doesn't work, then i'm really not sure what you should do. Sorry to not be much help.