Well, there are many egg mechanics that have changed, but you're dilemma is definitely abnormal. It can't be something that major, so just walk around with the 'walked' egg and hopefully everything should be normal up to then. Or, you may have just gotten the eggs mixed up. Lol. x)
As for your Hidden Ability question:
If you have a male Hidden Ability Pokemon then breed it with a Ditto, and there is a slight chance (not 100% chance) that the Hidden Ability will be passed down.
If you have a female Hidden Ability Pokemon then breed it with a male Pokemon from the same egg group. It will be a 60% chance that the Hidden Ability will be passed down.
There aren't many good tips as to breeding hidden abilities, I guess. I guess all I can say is that you can find Hidden Ability Pokemon in the Friend Safari and in hordes, 'cos otherwise there are no items that will increase the chance.
Hope I helped. :)
Source and Experience
