First thought is to look at the Channels Panel. Are all channels selected or is it one or two? RGB should all be visible.
Layers Panel: Make sure all your layers are in order and have the proper blend modes.
If that is not the case,
Here is a PSD recovery Utility:
If this does not help,
The other thing I would look at is recovering a past copy.
Shadow Explorer if you are on Windows and your file is kept on a C: or D: drive and Time Machine if you own a Mac.