When a URL ends with a ")", it gets stripped off the link (that is, it is treated as if it where a "]") -- this occurs in the text of the "About" of a profile.
I have not checked if the same is true for a Project's "Description" field.
Here is an example profile: http://www.geni.com/people/Sir-John-Mundy-Knt-Lord-Mayor-of-London/6000000010018532821 ... and the corresponding Wikipedia link that "breaks" in the "About": http://en.wikipedia.org/wiki/John_Mundy_(mayor)