Now, before anyone says "Move to Technical Issues", this isn't regarding Spiral Knights in the problem. I was playing Spiral Knights at around 8:00 PM EST, and then logged off SK and Steam at about that time. I watched Men in Black 2 for a couple of hours :3. Then I decided to go back on Spiral Knights to check an auction and get this: http://oi49.tinypic.com/2i1z62q.jpg . I tried to re-install Steam a couple of times, I looked at the Steam forums (which look foreign to me, as I've never used them). There are solutions I've heard, that worked for some, but what about for a Mac? Anyone else having this problem?
Note: After re-installation, it said I needed to be in online mode to update.

Edit: So you know: This is regarding the Application on the computer, not the online (website).