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You run a Windows Presentation Foundation (WPF)-based application on a computer that has Microsoft .NET Framework 3.5 installed. When a TextBox control of the application receives the focus, a NullReferenceException exception may occur that causes the application to crash.
This issue occurs because the Input Method Editor (IME) mode of the TextBox control enters a state that causes a NullReferenceException exception when it receives a notification from the TextBox control.
Note This notification is sent after the TextBox control receives the focus.
To resolve this issue, apply the hotfix package that is described in the following Microsoft Knowledge Base article:
2667241 An update rollup is available for Windows Presentation Foundation (WPF) for Microsoft .NET Framework 3.5
To work around this problem, turn off the advanced text services.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates