Last night I was playing some games on Steam and closed it after I finished playing. Then I browsed around the Humble Bundle and bought the 'Humble Indie Bundle 9' since I wanted 'Mark of the Ninja', so to redeem it I switched on Steam. But it wasn't starting up. So, opened it from terminal and got some errors, but those were there since ages and doesn't actually affected the start up last time.
So, this morning, I was talking to a friend on IRC about it and he mentioned that you could just do
/usr/bin/steam --resetto reinstall and start again..and voilà it was indeed working again. :)
[Note]: Another friend suggested to restart the router, not sure how effective that would have been though. :P