If you join a game that has been running for some time, it plays through it as fast as your PC allows. Then if you catch up with , it will continue at real time. However, if the game ends before you catch up, you will get this disconnect error. In short, everything seems to be working fine there! :)
PlanetWars is a turn based game on top of the RTS game, where you can fight over planets one battle at a time. It's probably best to watch a few games first, and play a few regular games so you know how everything works. Then join PW when you feel comfortable with the game.
As far as missions go, I recommend 2v1. It allows you to learn the game in a nice and easy way.