Current:            10.3.20103.1000
New:                  10.3.20103.2083  (I think this is correct. Whatever SP is out there right now)

Yes, I used the upgrade facility.

I ended up rebuilding the form.

Hello ,

I guess that you are using UltraToolbarsManager in your application, because usually UltraToolbarsManager adds frmMain_Fill_Panel to the form. Also I suppose that you get this exception from Designer.cs file. I have tried to reproduce your issue (to get this line of code that you are posted in the designer file) with upgrading of a small sample from 10.30SR 1000 to 10.3 SR 2083, but I was not able to get this line of code in my designer file. So I add it manually and, just then I was able to reproduce you’re the mentioned behavior. So if you remove or comment this code line everything should work. But the question is how this line appeared in your designer file? Please try my suggestion and let me know for the results, also if is possible could you please  tell me if you manually add this line of code for some reason.

I am waiting for your response.

Mark this as closed since I rebuilt the whole form. I didn't have time due to a conference deadline so I had to act immediately.

Hello,

Thank you for provided feedback. I am glad to hear that you were able to solve your issue. Please let me know if there is anything further that I could do for you.

Thank you .

did you ever figure this out. it is similar to a problem I'm having.

Im having a very similar problem

Error

The Controls collection of the UltraPanel is read-only.  Modify the UltraPanel.ClientArea.Controls collection instead.

line called out 

this.panel1.Controls.add(this.panel1.ClientArea);

Hi,

I Put this line out and the error is gone ?

'Me.Customer_Fill_Panel_1.Controls.Add(Me.Customer_Fill_Panel_1.ClientArea)

Francois

I had the same problem after upgrade version 12 to 13.

What can I do for resolve the problem ?

Francois