Apple has now begun reissuing OS X Mountain Lion redemption codes to customers eligible for its free up-to-date program. These codes replace those issued to customers earlier today, which had already been redeemed, according to the Mac App Store.
A handful of readers contacted Cult of Mac earlier today to report that the redemption codes they received for Mountain Lion were invalid. The Mac App Store told them they had already been redeemed.
Those who contacted Apple were told that the company was aware of the issue, and that it would be resolved this afternoon. It now appears that those affected are receiving replacement codes, which should work perfectly — fingers crossed!