Try trashing your Photoshop preferences. Press and hold Alt+Control+Shift (Windows) or Option+Command+Shift (Mac OS) immediately after launching Photoshop. You will be prompted to delete the current settings.
(Mac OS only) Open the Preferences folder in the Library folder, and drag the Adobe Photoshop CS Settings folder to the Trash.
This action only affects the items found in the preferences dialog box. Numerous program settings are stored in the Adobe Photoshop Preferences file, including general display options, file-saving options, performance options, cursor options, transparency options, type options, and options for plug‑ins and scratch disks. Brushes (and lots of other setting) are not affected by the above instructions for deleting preferences. You may wish to make a screen capture of the settings in the Preferences dialog to reset them prior to deleting of this file.