I tried putting your provided example as follows inside a script block
This throws a NullReferenceException when attempting to reference the Details Panel in the FindControl method
Also, reading your code block I am a little uncertain why your getting reference the the panelBar and the item and then just calling document.getElemenentById.
This does need to be in a telerik:radscriptblock to evaluate at runtime correct?
And this solution still does not answer the question why I can reference a telerik control inside a template but not a asp control.
Could you provide an example where your javascript is accessing a regualr asp item such as a div and changing the innerHTML property through Javascript clientside.
Thanks for the Help,
Andrew