I have been able to reproduce this in a new project. I was actually testing this it in our QSF example of RadListBox when I wrote you previously. The issue seems to be related to our Theming mechanism.
We will do our best to fix this for the coming Service Pack release scheduled for the end of the month.
However as soon as I prepare a working .xml file with a new theme for RadListBox I will send it to you and the problem will be fixed.
At the moment I can suggest you a little patch which will visually make the control to appear as expected. Follow the steps:
1. Subscribe to the ValueChanged event of the listbox control
RadScrollLayoutPanel panel = listBox.ListBoxElement.Children as RadScrollLayoutPanel;
panel.VerticalScrollBar.ValueChanged += new EventHandler(VerticalScrollBar_ValueChanged);
2. Refresh the Selection state of the selected listbox item
RadListBox listBox = (RadListBox)this.Controls;
RadListBoxItem item = listBox.SelectedItem as RadListBoxItem;
Thank you for the feedback.
I have added telerik points to your account for this bug report.
the Telerik team