Detailed COM Interface error

[katak]

I am using .net C# to call a third party application to edit a .xml file.

This is the error the third party application return when I tried to save
after edit.

Unalble to save: failure writing new data to object tree.
Detailed COM Interface error: 80004005

Then I tried to directly run the third party app to save the .xml but it
returns me the same error as aboved. So I suspect the problem due to the
..xml file itself.

This is the line that caused the error:
<PCInterface xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

After I removed the xmlns and keep <PCInteface>, problem solved.
This is a XML file given to me. What can I do to eliminate this problem
without changing the file?