We are not aware of such IE9 bug and haven't meet it in our implementations with RadAjax controls.
If it is convenient for you could you please open a regular support ticket and send us sample runnable application which demonstrates the issue after ajax request using some of our RadAjax components.
Thus we will be able to further research on the problem and provide any statement if there is any possible workaround we could implement.
the Telerik team
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