I have the same problem as the user in the link bellow, but his post was never answered.
I thought this issue was a bug in eagle version 6.5 but the same problem persists in version 6.6.
The only way to export a monochrome correctly without the tracks showing inside the pads is by using eagle 6.4.
Why this problem was not addressed in eagle 6.6?
Thanks in advance.
http://www.element14.com/community/thread/28480/l/pcb-image-export-problem