Sounds like this may be a performance issue. How complicated is the contents of your Scroller? Do you know if your application also doesn't scroll smoothly on Android?
Ya as I said that I am using 10 skinnable containers and in each of the containers I am having 4 Labelfield and an image.
So I dont think this is becoming too heavy for the device to handle.
Can this be a problem because I am using MXML components for Customizing the skinnable component???
Should I go with Actionscript for customization???
In general I have found performance on BlackBerry PlayBook to be very good, but it's still not going to be as fast as a powerful desktop computer. If the contents of your SkinnableContainers are unnecssarily complicated that might have a negative effect. Have you tried this on an Android device to see how it compares?
Moving from MXML skins to ActionScript skins will result in better performance. Check out this presentation for some general guidelines and tips on optimizing your Flex applications.
Flex doesn't officially support BlackBerry PlayBook yet (coming shortly) so it's possible that the build you are using isn't optimized yet. If you would like you can send me your project and I can investigate a little further on the latest builds.