"'Are your days like those of a mortal or your years like those of a strong man, that you must search out my faults and probe after my sin - though you know that I am not guilty and that no one can rescue me from your hand?'" NIV translation
In effect, Job is basically asking God if He does not have anything better to do than to bother Job. He goes on to assert his innocence but, once again, Job has lost sight of the fact that the very act of questioning God's justice and mercy is a sin caused by pride.
In this pride, Job makes it sound like God has to really do some long searching to find something against him to justify what he sees as this punishment from God. He begins to defend himself but what he really needs is a dose of humility and that can only be attained through experience.
Up to this point, Job has had hope in a religion (his own works) but, now that that hope has been taken away, he is in a position where he can begin to see that his only true hope comes from the work of God. At the heart of humility is the realization that we do not have the power to do something for ourselves. Job is getting to this point but only after he has gone into the valley of despair.