Right when I needed to make a change in a hurry to a BAM Activity, I started throwing an "Unspecified Automation Error" on two of my three development machines when launching Excel with the BAM add-in.  Excel would launch, throw the error, then launch a VBA window.  While I got my change in on the third (unaffected) machine, I finally got some time to circle back to this.  From the post below, a recent patch caused this issue, but at least it's understood and only requires re-registering MSCOMCTL.OCX.

http://blogs.technet.com/b/the_microsoft_excel_support_team_blog/archive/2012/08/15/quot-unspecified-automation-error-quot-after-applying-ms12-060.aspx