My friend, a player known as "Bearwolf" (also a member of my guild) told me today to join his party because he was "scared". I joined it when he was on depth 7 green eagle gate I believe, thinking it was a joke, however as soon as I clicked the "join" drop down button it immediately logged me out. When I tried to log back in, it said:
"We have experienced a problem authenticating with Steam. Please ensure that the Steam client is running and that you are not logged in elsewhere."
This is very strange. I have no idea what to do and just want to get my account back. My account name is "Secure" in-game and my steam account username is "darkbyte97". Could he have Hijacked my in-game account from my steam account? Or make it go to his steam account? I don't know but I have spent time and money on this game, and really do NOT want my account to be gone forever. This is just what sounds like happened, since it says Im logged in "elsewhere". I have no idea what actually happened and I just want my account back as stated many times before...
I did immediately change my steam password though. I don't know if that has an effect on anything.
Did you try closing steam and restarting it? I mean exit steam completely. Or reboot PC.
Then restart Steam.
I had exactly same problem - lost connection, was disconnected, upon retrying connection I couldn't log in with my steam account, error message was the same as yours. I restarted the game - same error. Upon restarting Steam it all worked again.