Invalid packet 12 is when the .mis file for a map you load is not able to find the texture to the skybox. This may be caused by the file locations not be correct. In order to fix, redownload the map and follow the instructions exactly when unpackaging it. Most maps will only require you to extract the map to your main Blockland directory. Failure to follow intructions for download may result in getting an invalid packet 12 if the map uses one of the default sky textures or ones from another map.
