Mayor flaw in Islam?

I don't want to seem offensive to other religions, but I once read a comment someone made disproving Islam. As you know, the Q'aran mentions Jesus loads, but only as a prophet. Jesus of course was known to many as the son of God, and part of God. This is undeniable because he even said this himself. The flaw is, that as a prophet of God, how would he be able to lie about being God in human form. This would've been blasphemy of the highest order, and as a prophet (or so believed) he wouldn't be able to lie, as it is a grave sin. I don't know if I wrote this completely correctly, but can anyone support/deny this?