I want to be clear, this is an issue I have seen in older versions, but wanted to provide feedback as the issue still exists in the latest beta as well.
I have a word document with many EPS images inserted, and a background "paper colour" as black.
The rendering of one of my EPS images is not proper when using the built-in PDF file generator in MS Word 2010, and using the PDFCreator printer driver provides what seems to be a perfect job rendering the EPS within the PDF file, but seems to mishandle the background colour.
I tried to use a background image of a black rectangle, but the same thing occurred. My only guess is that the white color is being replaced with "clear" as an assumption that the background is white?
I can send a copy of the document if you like.