Hi Jorn,
I can confirm that SelectionStart does not work as expected after the official Q2 release. I've logged this issue in our PITS under the name
"Slider: Binding SelectionStart does not work as expected after Q2 2011" and we'll do our best to fix it for the upcoming Service Pack. As a workaround you can use the new Selection property.
Give it a try and let me know if it works for you. I've also updated your Telerik points accordingly.
Kind regards,
Kiril Stanoev
the Telerik team
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