I can not open Photoshop CC - My older Photoshop CS6 opens fine. But, I keep getting a message when I try to open Photoshop CC: "Could not complete your request the internal file signature is incorrect
Sounds like the file image on disk is corrupted. You may have to uninstall and reinstall.
You should also determine why it got corrupted, especially if it was once working without the error. That could mean you have a malware infection.
Is this a concern with new Gatekeeper on Mavericks?
It seems your copy of PS CC is corrupted now hence this message.
As Noel suggested please try uninstalling PS and then install it again from CC app.
After successful installation verify.