He is reported to have said that "Because there is a law such as gravity, the universe can and will create itself from nothing....Spontaneous creation is the reason there is something rather than nothing, why the universe exists, why we exist...It is not necessary to invoke God to light the blue touch paper and set the universe going."
What is wrong with this? Well it doesn't explain the temporal order of the universe, or why there is a law of gravity in the first place. The statement 'Spontaneous creation is the reason there is something...' is also circular and not explanatory because he is trying to explain the origin of the universe from something within the universe. It doesn't explain where the law of gravity came from and it is really no different than an appeal to magic in that it seeks to give creation creative power over itself. This is a classic pagan claim.
Hawking also needs to explain his own mind and intellect if we are to consider it trustworthy. If we reduce our minds to atoms then our thoughts become meaningless. Perhaps Hawking is shaking a metaphorical fist at God by trying to prove he doesn't exist, but Hawking has spiritual needs as well. We need to pray for him. Also see this blog entry by Andrew Halloway