Since Telerik did not "deliver more than expected" with your last response, I decided I was on my own to resolve the issue and tried a long shot. Contrary to your statement "... I don't know of such problem with the previous version either.", there apparently is a glitch.
I upgraded to "2008.2.1001.20" and scrolling works fine.
It also had worked back in July when I did a cursory test with 2008.2.723. I set the test aside while I hosed out other fires. The dev team upgraded to 2008.2.804.20 at some point between then and now and it is that verision that seems to have an issue with scrolling.