I've been using your Oauth library for a few months now and am very please with it. I often find setting up Oauth 1 apps a challenge. After struggling with LinkedIn for some time, I modified the library to use Oauth2 for LinkedIn and all my problems went away. In addition to modifying Initialize(), I also had to create some wrapper functions in my sub-classes (I created sub-classed oauth_client.php for each of my social channels) that append the access_token to the end of the endpoint URLs for the user profile and connections (friends).
Curious, I also needed to put some 'exit' commands inside process() just after "$this->exit = true" lines for both v1 and v2. I've included your library into a CakePHP shell as Cake Libraries inside it's Lib directory. I assume that has something to do with it. Any thoughts?