Thank you for the report.
Quite a few users experienced problems with the GPG setup, and the reason remains unknown.
I already identified a bug in the php gnupg bindings when using raw key format, so i switched to ascii armor only.
For your case, it might be that the GNUPG version does matter, or maybe the keychain can not get resolved completely.
Sadly the gpg error messages are not very helpful: "encryption failed" is all i can get from it
If i find some spare time and mood i might check into it deeper.