I have an Ipod photo which did exactly what you are saying has happened to you.
Have you downloaded the official update from apple.com ?
As the software which comes with the ipod is out of date.
You do not need an ac adaptor as the ipod will charge up whilst you are on your laptop but if you are not using the laptop then 'Yes' you will need ac adaptor
I would say the ipod as a whole can be tricky sometimes as 9/10 it will not update.
It can be annoying but if you are not happy return the item.
But mine is running fine and is probably 1 of the best out there.
Hope it helps