I agree, "cast". A cloud casts a shadow; a fisherman casts a net. "cast a cloud" is a little odd to me because I think of "cast" as similar to "throw" and throwing clouds seems like a futile pastime, but "cast" works and "cost" doesn't work at all.
There are thousands of examples of "cast a cloud" via Google, mimi2. I think it's a common expression. "Cast a pall" is more common, as is "cast a shadow." I think I would use "cast a shadow." I can't think of a more appropriate verb with "cloud".