PrintDialog.ShowDialog(this) immediately returns DialogResult.Cancel on Windows 7

An in house application that I'm developing is behaving strange on a Windows 7 (64 bit) PC.

If I create an instance of a PrintDialog, and call it's ShowDialog() method, the method immediately returns DialogResult.Cancel without showing the printer dialog form.

The Windows 7 PC does have printers installed (with a working default printer).

PrintDialog printDialog = new PrintD开发者_开发问答ialog();

printDialog.PrinterSettings.Copies = 2;
printDialog.AllowCurrentPage = false;
printDialog.AllowPrintToFile = false;
printDialog.AllowSelection = false;
printDialog.AllowSomePages = false;
DialogResult dialogResult = printDialog.ShowDialog(this);

if (dialogResult == DialogResult.Cancel)
    return;

Any clues why this is happening?

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Set printDialog.UseEXDialog to true to work around this bug.

In .Net 3.5, MSDN mentions this potential problem when documenting UseEXDialog:

When this property is set to true, ShowHelp and ShowNetwork will be ignored as these properties were made obsolete for Windows 2000 and later versions of Windows. Also, The PrintDialog class may not work on AMD64 microprocessors unless you set the UseEXDialog property to true.

(My emphasis.)

The same page for .Net 4 and .Net 4.5 don't include the emphasized bit, so perhaps it's fixed in those versions.