"Could not open"filename.psd" because the file is not compatible with this version of Photoshop"

I was working on a file yesterday and saved and closed it at the end of the day. I did not turn off my computer or update Photoshop (that I know of at least). Today when I got into the office I tried to open the same file and get the error message "Could not open"filename.psd" because the file is not compatible with this version of Photoshop".

I was literally working on this file YESTERDAY in the same version of Photoshop!! What gives?!

Things I have tried so far:

• restarted my machine
• uninstalled and reinstalled Photoshop
• uninstalled and reinstalled different version of Photoshop
• opened a different file in Photoshop (which works)