If a person is saying that he is lying, then how would you consider it a lie or a truth?
I suppose this is supposed to be one of those paradoxes where if they are lying about lying they are telling the truth and if they are being truthful about lying then it is a lie. But really it is a pointless, useless statement so the veracity of the statement is irrelevant.
However, I tend to sit on the side of lying because there are many ways to lie so lying about lying doesn't necessarily mean your telling the truth (eg. there can be half-truths or lies of omission or misdirection etc... ).
You have snuck up on Gödel's incompleteness theorem as applied to the 'Liar's Paradox' - The liar paradox is the sentence "This sentence is false." An analysis of the liar sentence shows that it cannot be true (for then, as it asserts, it is false), nor can it be false (for then, it is true). A Gödel sentence G for a theory T makes a similar assertion to the liar sentence, but with truth replaced by provability so you can replace provability with truth. Philosophy and logic can often be stated in terms that look very like mathematical formulae. It can be restated as:
Thus the following two statements are equivalent:
This statement is false.
This statement is true and this statement is false.