Keep in mind that BI is a "one man band", so Ken can e pretty busy and technical questions, like this, may take some time to get answers for. I assume you have a current support subscription, as well. I recently asked a rather mundane question that "normal" support could handle and that to took days to get an answer for. Patience is a virtue, but frustrating I know.
You could run ProcMon and then monitor what the BI installer is doing? Be warned it will generate loads and loads and loads of data but start the capture just before you kick off the install and then end the capture after the error message. You can then use filters to "view" the BI installer process to see what it might be looking for?