Somewhere on this forum I have suffered and solved just this issue. The problem is that the BB install looks for specific registry keys, actually the v7 Notes install one. Don't know if its v7 it's looking for or just the fact it's not seeing a v8 one. The solution is this:
Close Notes client
Edit registry entry HKCU/Software/Lotus/Notes/8.0 to be 7.0
Install the BB Manager
Rename registry key back.
Nothing to do with 4.1.4.
here's the link, Unable to Install Blackberry Manager