Thanks again for your reply!
I followed your example, and indeed, it worked!
However, when I try to apply what you suggested to my case (I bind the RadChart in CodeBehind), I got the following error message: "Bar series is not supported with client-side scrolling and zooming enabled."
I already solved that issue the following way:
BUT, unfortunately, I think I misunderstood the RadChart's scrolling functionality, because it seems it's ONLY available when I apply zoom to my chart, otherwise the scrollbar never shows. Am I right, or is there a way to use horizontal scrolling WITHOUT zooming?
ChartSeries serie = new ChartSeries("lines", ChartSeriesType.Line);