If God is omnipotent, can't He lie to us?

If God is [supposedly] infallible, omnipotent, yet INcapable of lying to us or betraying our faith... implying God does not have the power to be fallible, or have the choice to change His divine mind... should we not seriously re-examine our interpretation of God’s nature? (And perhaps even admit that God does not exist, or at least is not the God commonly believed to exist?)