Equations in a Document with DRM is not saved properly

[Lawrence]

When a word 2007 document containing an equation created with equation editor
is saved with access restriction, the document cannot be opened again.

Spec:
Windows XP SP2
Micrsoft Office Ultimate 2007
Using Microsoft Update, updated all components

Steps:
1) Install the necessary plugin for Office 2007 DRM funciontality (when you
want to apply permission restrictions, Office 2007 will require a plugin from
Microsoft)
2) In new Word 2007 instance, insert some plain text
3) Insert an equation into the document
4) Apply restrictions, giving yourself full control on the document
5) Save the document, and close it.
6) Open it again.

I recieve the follow error when I open it again:
The Office Open XML file This is an equation cannot be opened because there
are problems with the contents.

Details
Unspecified error

Any ideas what's wrong?

 

[Lawrence]

The equation must not be one of the "Built-in" ones (the ones that are
available when you click on the down-arrow on the Equation Icon).

Click on the Equation Icon, and insert a custom equation.

 

[Lawrence]

The equation must not be one of the built-in ones (the ones avaliable when
the down-arrow is pressed just below the Equation Icon).

Click on the Equation Icon under the Insert page, and insert a custom
equation.