I have three partitions: Mac1, Mac2 and Data. Suddenly Mac1 (my startup partition) has disappeared from the Finder and the desktop, and Spotlight doesn't find it. I can still get to it through my home folder though (column view and then use the path button or cmd clicking on the window title). However, whenever I actually see the Mac1 icon it is grayed out and I can't click on it. What's going on?

I had the same problem ,but the only way to resolve is by reinstall the os x
Just problem whit the mounting of the partition ...