Shortcuts issue. When changing tools via a shortcut, Photoshop responds slowly then snaps back to the previously selected tool. It is not tool specific (like the hand tool issue found in older posts & reports) as it just snaps back to which ever tool is selected previously. The issue only happens with larger files and follows the problem file between systems and Photoshop versions (CS4 and CS6). The two systems were iMacs, one running mountain lion, the other running lion. The issue does not happen when selecting the tools by clicking on them with the mouse on either system. Any help would be appreciated!