Hey Twitter guys, I had 2 lists. Both named "My Favstar.fm List". One with slug 'my-favstar-fm-list", and the other with slug "my-favstar-fm-list-8". (I'd created a few and deleted some with the same name). The list without the -8 suffix is the one I've been using in anger, and has 35 members.
I've just been in to twitter.com to edit the "my-favstar-fm-list" list, adding a description "My favourite tweeters from http:/favstar.fm". After the update, the slug was changed to "my-favstar-fm-list-8". So I now have 2 lists with the slug "my-favstar-fm-list". (IDs: 126147, 968546) Eeep. Tim.