I was working on a project in Adobe Illustraor (CS5) and suddenly all of my work disappeared. Help?

I can still select everything that's in the document, I haven't lost anything, but I can't see anything unless I've selected it. I'm not a n00b at Illustrator, so it's not like I've turned a layer off or I've turned the color off... I have tried copy and pasting, I've tried restarting my computer, I've tried changing the colors of all the objects, nothing is working. Any suggestions would be very helpful.