If a server is already running on port 4242, a local game will fail during world creation. The error message doesn't specify what happened or why it failed. It would be good if the game tested if port 4242 and give a proper error message to that effect rather than an "uh oh.. something bad happened."
I also saw these weird messages when running .200.122 from a clean install:
[TEXTURE-PACK] WARNING: ignoring shield_tex.png: not a directory
[TEXTURE-PACK] WARNING: ignoring shield_tex.png.zip: not a directory
[TEXTURE-PACK] WARNING: ignoring lava.png.zip: not a directory
[TEXTURE-PACK] WARNING: ignoring lava.png: not a directory
[TEXTURE-PACK] WARNING: ignoring shield_tex.png: not a directory
[TEXTURE-PACK] WARNING: ignoring shield_tex.png.zip: not a directory
[TEXTURE-PACK] WARNING: ignoring lava.png.zip: not a directory
[TEXTURE-PACK] WARNING: ignoring lava.png: not a directory