I ran into an issue with the RadSpreadsheet control embedded in a RadWizard step. The control would appear on the screen with an empty cell area, no grid and no data. I could verify the file was loaded properly because the data in cell A1 could be seen in the Formula Bar. Resizing the browser window in any way would immediately trigger the control to refresh and everything looked great, but not until then. I contacted Telerik Support and Peter Milchev very quickly responded with the following:
"The problem with the Spreadsheet appearance is due to the fact that
the control's container is initially hidden, hence the calculations are
We have researched a bit and it turns out the behavior can be further improved and the control could handle itself a hidden parent container.
Until that becomes a part of the source code, please verify that adding the following script Under the ScriptManager would fix the issue."
The workaround resolved the issue immediately. I hope this helps you as much as it helped me.