XML Write problems

[martys]

While attempting to using XML Write, I came across an annoying problem: Whenever I try to execute the step, it says "Error at line 3, position 11 loading 'file.xml': DTD is prohibited."

What exactly does this mean? How do I get around it without permanently modifying the XML file? I know the DTD is valid, because I can open it in Firefox, IE, and Visual studio, all with no complaints.