So namida just posted a bug involving pickup skills that triggers an error message. I'm getting a similar sort of thing here which according to the level doesn't have any pickup skills at all, but instead had several updrafts, and pre-assigned gliders.
Basically, the error message pops up when loading this level in the editor, but is still playable in the player. It can be found the "War" rank of the "Lemmings United".