See http://wiki.processing.org/w/Changes P2D and P3D modes are prone to disappear in Processing 2.0, and you elected an unstable version, close of 2.0. Either go back to 1.5.1 or ask the proScene authors to update their library.
Yes, I'd say that all pre-releases after 198 are mainly intended for testing purposes. Many things that used to work before, particularly libraries that depend on the renderers, might not work anymore.
For production work, it is probably recommended to stick to 1.5.1 for the time being.