Homosexuality is, according to the Church's moral teaching "intrinsically disordered".
Homosexuality is a mental/emotional defect that cannot be tolerated in an ordinand.
Joaquin Navaro-Valls (sp?) said something very interesting recently, that I read in "Our Sunday Visitor". He said this could be grounds to possibly annul the ordination. I don't know what this really means theologically, but you know the Vatican is looking into something.