There seems to be an issue on both twitter.com and the lists API for users with large lists.
For example go to https://twitter.com/virginiawillis/lists and try clicking on the “foodies” list. The url is incorrect and goes to //lists/foodies. If you correct the url as https://twitter.com/virginiawillis/lists/foodies then we get a 404 page not found.
This seems to happen for all of the user’s owned lists. In a related issue none of the user’s owned lists appear in the get/lists/lists request.
I haven’t seen this issue reported anywhere else. Please take a look.