So yeah there's an issue and counsel is looking into it, but we've made some progress.

We're pretty sure that the coding to create the transparency in the source slide for 2003 was done in VBA somewhere in the PPT coding.

This means that in order to get that to work in 2007 it needs to be done in XML. However there doesn't seem to be a code for transparent in XML as there is in VBA (which funny enough is simply "transparent")