Could you please explain in detail what you mean by saying that the server event of the RadSlider does not work? Do you get an error, does the RadSlider not postback the page or does your code in the server handler not get executed?
I created a simple test page, based on the code fragment you posted, but the server event of the RadSlider controls did fire and the code that I put in that handler did get executed. I have attached my test page for your reference. As you have not specified which version of the suite you use, I tested with the latest - 2009.1.402.
In case you still have problems with the server event of the RadSlider, please prepare and send us a simple running project, demonstrating the problem. Please note that as you cannot attach files in the forums, you have to open a new support ticket in order to send us the project.
the Telerik team