Obout.com ComboBox "Failed to load viewstate" error

I have just downloaded Obout.com suite controls for ASP.NET 3.5 and 4.0. I made this because I wanted a DropDown with images near items.

It is working well, but, still in the examples, when you set AutoPostBack property to true, and you select an item from the ComboBox controls you get the following error:

"Failed to load viewstate. The control tree into which viewstate is being loaded must match the control tree that was used to save viewstate during the previous request. For example, when adding controls dynamically, the cont开发者_运维技巧rols added during a post-back must match the type and position of the controls added during the initial request."

I'm using VS2010 Ultimate Edition,

Any help would be greatly appreciated!

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Never used that suite but can recommend a good alternative: Image Combobox Jquery plugin. Thus you'll be able to use the standard ASP.NET DropDownList control.