sigh. It ate my reply. Having horrible success with Apple today :(. Trying to rewrite it from memory:
I can load the extension. I have another network extension in the app -- a transparent proxy provider, while this new one is a content filter provider. I can save the preferences for the TPP, but when I try to save it for the packet filter extension, I get permission denied (error 10). The application is in /Applications
(thus allowing both extensions to load). Quinn's debug post does not cover that issue.
I had a test program that worked, but after the issues (described elsewhere today) with my Developer ID Application certificate, I can't build it at all anymore. And Xcode keeps revoking my certificate because the private key isn't in a keychain, which does nothing, so it keeps trying to do that, and I can't get it back to building.
sob