I have to admit I had not tried to use the Wish List feature before this. After reading your post, I went in and tried to use it and got the same results you did. I sent a message to one of the LL moderators to see if they can unravel the mystery for you. LL has recently redone their site and it may just be a little glitch that needs fixing.
Wish Trips is a fantastic tool...when it works! Unfortunately with all the recent changes that have been happening with the site, Wish Trips and My Account have had to take a backseat. However, they are on the radar to not only have back up and running, but to become a very fun and useful tool for LL members.