Using xsi:nil in XML

I am generating an XML file from a VB.NET app. The document was generating fine before I tried to add nillable elements. I am now testing putting i开发者_Go百科n just one nil element as:

<blah xsi:nil="true"></blah>

Once this element is in place and I try to view the XML file in IE it is unable to display. I am receiving:

The XML page cannot be displayed Cannot view XML input using XSL style sheet. Please correct the error and then click the Refresh button, or try again later.

---

The operation completed successfully. Error processing resource

If I remove this one element it displays fine again. What am I missing here?

Do you have xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" to declare the xsi namespace set on the root element of your XML?