Hi there thanks for the bug report
I saw the same error (java.lang.NoClassDefFoundError: org/terasology/world/generation/facets/SurfaceDepthFacet) get reported on IRC the other day, was that you by chance?
That error usually comes about from modules building out of order, or version mismatches between modules and/or the engine.
As per the logs you're using the latest stable release, Alpha 6, but by chance did you update some of the modules, like via in-game module browser?
If you updated modules that way it could explain why local single player fails (using the updated modules) yet multiplayer against a server works (the server determines which module versions to use)