Please view the attached screen shot.

We have a web form (in sharepoint) that has a parent question of radiobuttonlist type. Based on the option selected we make a div visible below the question that displays a question with a radcombobox control. Please note we are simply toggling the div that shows the combobox via javascript so it exists in the mark up at all times.

The combobox is loaded on demand. However when we click on the combobox to load the items on demand we get the error in the screen shot. I can see that the target does exist in the html markup.

If we replace the radio button control with a dropdownlist and keep everything else the same then it works perfectly. The problem only seems to occur when we use it with a radio button list.

The other odd thing I have noticed is that if the radio button is loaded with an option selected then everything works perfectly. It only seems to happen if the radio button has no option selected when the page loads.

I have tried to create a web project to demonstrate this however I have not been able to recreate the problem. The problem is that our solution is very complex and to replicate the exact scenario in a web project in its simplest form might be very difficult and time consuming.                                                                                                        
The only thing I can suggest is that I can give you access to our system. I have implemented the combobox with load on demand as per your recommended approach.             

Sorry forgot to attach the file.

Hello jasear,

I would like to ask you to provide us with the implementation of the RadComboBox, the exact approach that you use for population with data and the logic for hiding/displaying the mentioned div. Thus we could try to replicate the faced issue locally and provide you with the proper solution.

Regards,
Nencho
Telerik