FlexUnitApplication not being generated properly

I'm trying to use flexUnit, but I'm running into a problem. When I go to executeFlexUnit Tests, I encounter the compiler error: "Content is not allowed in prolog"

The FlexUnitApplication.mxml file that gets generated looks like this:

<!-- This is an auto generated file and is not intended for modification. -->

package_declaration
{
class_declaration
{
class_body
}
}

Can anyone tell me how to fix this, or where to look for the files involved?

I'm using the FlashBuilder 4 plugin for eclipse on Windows.  SDK version 4.0.14159