Problems with XAML WPF 4.0 Editor in VS2010

Wondering if anybody else has found some very odd behaviour with the XAML/WPF 4 editor in VS2010, and can explain what is going wrong. This only occurs if the project is using .NET 4.

Whenever I tried to open a XAML document for editing, the window would appear to open for a split second and then vanish, but VS2010 would still list the window as open.

The fault was eventually traced to having the "Reuse current document window, if saved" option und开发者_运维知识库er "Documents" in the "Environment" options checked. Once this was unchecked XAML 4 files opened as expected.

As I said, this only appears to occur on projects targeted at .NET Framework 4 - those targeted at 3.5 worked without a problem, and the "Reuse current document window, if saved" appears to work fine on other files.

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