Mac OS X 10.8.4
I've rebooted a couple of times, and uninstalled/reinstalled via the CC Control Panel. Even more comical is when I try to retrieve information about my installation I get this error from the Adobe CC site: We're sorry, something seems to be wrong on our end. Please try again later.
Not sure if this helps, but might be worth looking into (I had some issues with Illustrator yesterday after upgrading from CS4)
Could it be a Firewall issue? Try disconnecting from internet?
Thanks for the suggestion. I disconnected and fired up Photoshop, and this time, while it took longer than usual, it did open up!
Then I got back online, shut down and opened again, and worked. Not sure what the deal was, but something was stuck with regard to being online.