Windows 7 you need to open Sonar as admin too.
I had the same problem, and someone at Cakewalk suggested this, and it fixed it. I set up Sonar to always run as admin, then after months realised that I hadn't used Pentagon. I then read an article on using Pentagon as a vocoder and gave it a try. Had great fun for a bit, but then had a major crash. I'm not saying it was Pentagon, but my system has been ultra-stable, so have not used it since. Will try again sometime, I suppose.
Edit for spelling....