Confused.com?

I have purchased a 2011 satnav disc from the web, but it eventually says 'Disc Read Error' I have tried cleaning the lens, albeit with the ruler method. But if I insert the old disc the satnav works which suggests the laser is clean??? I have tried to force a download, screen goes black and eventually returns in the same state.
Would it be worth taking the unit out to have a good clean?
Any advice would be much appreciated