Title says it all. I can't save the mission I'm working on, while following the walkthrough.

I have this issue too

My saving works fine.

I've had some issues with this too. I keep wondering if my map's gotten corrupted, or if the server is just flooded.

The error messages could use to be a bit more detailled. "an error occurred" is kind of vague.

Prob the server.

btw: My roommate just disconnected from the serverafter about 3000 secs of showing 'server not responding'

This is partially caused by the servers being hammered by tons of players. Being the prettiest girl at the dance (metaphorically) means your feet will probably hurt by the end of the night.

It may also be related to an old bug that was mostly patched that corrupts a character.

Try creating another character (don't worry, your mission is still safe) and testing with that.