Just be positive and take it as an extra lesson since I believe that you did good job overall. There are always spaces to improve for everyone. Some people are luckily to be beat up to improve and others are not.
I got a bad score too but I learnt a lot out of it. I was shocked when I saw my score for 2008 and was very upset. Certainly, my manager was so mean that he made up many untrue things in my review. Actually, it led me to quit my job although I don’t regret and still think it is good time to take a break and take care of other things in lift too. Now, I found another better fit job.
With time moving on, although I still believe that I have no problem with my technique skills and work, I started to realize that I was poor at my soft skills and communication skills which can be more important than work sometimes. Plus, we are Chinese and something we think it is good to do under our culture might not the case under American culture.
I think that your managers are nice and at least they seem sorry about it and want to help you improve. You will impress them by being a positive person.
BTW, I was a single mom with a kid not long ago and it is good to be positive and keep job under this economy.
Good luck and keep uo posted when you have time.