This happens whenever your PS3 freezes. I used to use the browser on occasion, and freezing was a common problem for me. This scan was introduced in one of the last PS3 updates. It made me crap my pants at first.
I was playing with a friend last night who had been updating an lbp1 level and giving it a makeover with lbp2 logic. She said that one day the level just became unplayable and started to crash the PS3 anytime she tried to load it. I asked her to show me and sure enough it crashed my PS3 just like she said.
Well after hard resetting I received a very disturbing message stating "The file system of the hard disk may be corrupted. The system will restart, check the file system and restore it if it is corrupted". I have NEVER seen anything like this before on the many occasions that I have had to hard reset my PS3 over the years. Quite frankly it scared the heck out of me.
I started to get this message after the firmware update that added the stupid warning message every time you boot up your PS3. My PS3 freezes fairly often when I'd play BF2, play with a friend that spent his life playing with glitches LBP2, or attempt to use the internet browser back when it was pretty much unusable before they updated it. I think you should probably expect to see this message from now on when you boot up your PS3 after it freezes.
Levels: Sleeper Hits, Typewriter Tool Freestyle, QuikSlik Browser. CISARU: The Cyber Ninja, Pro_Go With The Flo. Upcoming: Star Trek: Futile Resistance.