This person is my 23rd great grandmother, but when I go to her father, he becomes my uncle, so there's definitely a snag here.
This is what it came up with today for me. Gilbert de Clare, 4th Earl of Hertford, 5th Earl of Gloucester is your 24th great grandfather.
May try it again.
http://www.geni.com/projects/Working-with-Relationships/17570