The "Could not access VBScript run time for custom action" error: I had this same issue on an SBS2008 server. In reading the notes of this post, I noticed that the same steps were taken. Specifically that Avast 4.8 was removed on both this server and mine. I thought that maybe that could be the issue, and it was. I reinstalled the server version of 4.8 on my SBS2008 and launched the BPP installer without issue.
Summary - if you remove 4.8 you will get that VBScript error installing BPP.
