But you don't have to guess. I've already told you it's wrong!
I think that there is a bit confusion and misunderstanding between the contributors and me.
I think I must say that "I'm sure of arriving." is not idiomatic because 'arriving' alone does not make sense and it needs some information of time or place, so that it is idiomatic to say, "I'm sure that I arrive there." As Raymotto pointed out, "I'm sure that I will arrive." is idiomatic because 'will' succeeded to make it sound correct by adding on time-information to the sentence.
I must also say thanks to all the contributors being kind enough to have answered my questions.