Was hired in Nov 2009 on salary - was NOT paid for 2 week period of closing during holidays of 2009; however, new person hired on salary Nov 2010 was paid for 2 week holiday closing in 2010. Can they do this legally?

Why don't you find out why you weren't paid in the first place first before taking the next step. You need to hear their side of the story before you try to defend this legally.

I have - I was told I was still on probationary period. I'm not sure why the same rules did not apply to new hire - guess she got to skip her probationary period?

Find out.

But if they said were on probationary period, then it's going to be difficult for you to argue against, even if they did something different for someone else. What did it say on your contract of employment?

Lastly, if you are paying union dues, then you should ask this question to your union.

How do you know company policy didn't change in 2010?
Is this a gov't or private employer?
I would be careful here.
Sure this new employee may have cut a deal, but that's none of your business at a private company. I can't imagine a company paying a brand new employee for 2 weeks of no work, but they may have felt she is very valuable. Or she may need a consistent check so took less pay. Or something... doesn't matter.