I ran TechTool Pro. And the surface scan reported about 40 bad blocks halfway through.
Apparently, Retrospect will back up files and give you a error log. Alternatively, dd will do the same, but quietly? I don't know. Downloading a demo of Retrospect. Am praying that read errors aren't in too many important places.
I wonder how many are new... 'cause I know I had some bad blocks previously, but I don't recall if I backed / wiped the disk or not, or if I put it off until I finished the LiveJournal stuff (which... I haven't done anything for lately, bother..)
Article with details: http://rentzsch.com/notes/survivingIOErrors