So I created a very simple vertical scrollbar from 2 stretched rectangles (a thumb and a track). I also grouped a text field and a square together, that would make up the list items.
Next, I selected the scrollbar and the list item, and created a data list from them. When I tested the project, however, I could move the scrollbar without any problems, but the items in the list did not move. I also tried adding some more items to the list, which didn't help either.
Then i tried using the component from Flash Catalyst, instead of my "home-made" scrollbar. Making a data list out of this, and testing the project gave the desired result.
I'd really like to use my own made scrollbar here, and I have the feeling that I missed something completely obvious on the way that I forgot.
Note: I checked several times if I had forgotton to "edit the parts" of the scrollbar and data list, but I had selected all the parts as required.
I had this problem once, and I realized I had converted my artwork to a Horizontal Slider component when I should have been using a Horizontal >Scrollbar<. I went back and converted the slider back to artwork, then converted it to a scrollbar, then made the data list and the scrolling feature worked.
What you can try if the above doesn't work, is deleting the scroll bar from your Data List, and then dropping it back in from the Library. The act of re-adding the scrollbar may get you the desired behavior.
If that doesn't work, you will probably need to post your project so we can take a look.