I had the same problem, and have just found the answer elsewhere on this forum.
It has worked perfectly for me. Here it is…
Just go to Users\Library\Preferences\Adobe Photoshop CS5\ and change the permissions on the folder. I just changed the "Everyone" variable to "Read & Write" and Photoshop started up without issue.
Thank you for such a quick response. It works for me too. Strange but it solves my problem. Now, all my customized Preference, Brushes & Workspace are saved as expected. Thank you again.
Your welcome, glad you got it fixed.
A year and a half later I had the same problem and thanks to your answer, problem solved. THanks very much.
8/6/2016 Same issue, Mac 10.10.5 Photoshop CC2015.5
Your solution worked as well.