Help! Server crashed. 'Kernel panic - not syncing: attempted to kill init! exitcode=0x00000007'

Our site is down. We’re running Ubuntu 12.0.04.3 x64. I haven’t changed or updated anything, and sometime tonight the site became inaccessible. I can’t ssh from my own machine but can access the console here. The last outputted line is the one above. I can’t copy & paste from the console page, but prior to that there’s a bunch of Buffer I/O errors, then ‘I/O error while writing superblock’, then ‘remounting file system read-only’, then ‘Core dump to |/usr/share/apport/apport 1 7 0 pipe failed’. (I’ve skipped a few in there…tried to highlight the phrases that seem important)

This seems bad, and I’m way out of my depth here…all the replies I can find on Google have to do with people attempting to install or update software, which I haven’t done. Help?!