Every time I start up my Macbook Pro 17 inch, I get this error. The last time my computer worked properly I successfully created a dvd with iDVD. Then it locked up and I had to restart. This error started popping up and I am unable to mount anything. If I plug in my iPod I get the same error and iTunes says it is corrupt. I would really appreciate any help I can get. Also, I'm pretty sure I've lost my start up disc.