Here is a bug I came across that is replicable on Mac as well as PC in Photoshop.
If you create a shape layer, say with the Rectangle tool, and then fill that shape with a default Photoshop pattern, in this example let's use the first one in the palette, "Right Diagonal Line 1". No problems so far.
Now if you double click the shape layer a "Pattern Fill" window comes up and you have the option to change the Angle as well as the Scale. Now in my testing, you can change the Angle, OR the Scale to anything and it's fine. BUT if you change BOTH, to various number combinations you can preview and continue to work and save the file as normal but then won't be able to open it back up again.
So to continue with the example:
I change my Angle to 64 and my Scale to 70
previews, save, close and when you open again, you get the error "Could not open "Untitled-1.psd" because of a program error.
Some Angle and Scale combinations don't seem to trip up and break the file, and/or some patterns may be immune from breaking.
As I said, it can be replicated on a PC besides a Mac and PC seems to create a log file when scaling that might have something to do with the error. Here it is below: