Please try to perform the steps given the following help article.
If it does not worked then try to reset the preference of Photoshop CC application.
Please check http://helpx.adobe.com/photoshop/kb/preference-file-functions-names-locations.html in order to reset Photoshop preferences.
Thnak you Sumit, but this did not help. Photoshop launches and a white box appears and then it just hangs.
Have you tried resetting preferences?
Could you please post a screenshot of current status.
Resolved. The white box also came up when I oppened Illustrator, but it filled in and asked me to my permission to provide feedback. I was able to complete the form and now Photoshop works.
It's trying to show a dialog, but isn't drawing correctly. Which OS version are you using?
If on MacOS, have you used a "system cleaner" utility? A couple of those are known to damage the OS and cause dialogs to not draw correctly.