MGM traded rights for the Spiderman franchise with Sony for CR67 and the rights to use the Casino Royale novel for a future film. Basically, in 1997, Sony announced they where re-readapting Thunderball. This lead to Sony and MGM having a franchise conflict (Sony wanted Spiderman to create a franchise, MGM didn't want the Bond series undermined by competition). Or at least this is what Wikipedia tells me.
I'm not sure if MGM got the rights to NSNA in this as well.