WE can't know. You have not provided any useful technical info like system specs and so on.
hmmm... i was hoping this was something common and easily recognizable. running CS4 on Mac 10.9.4. I just had the problem last night with a raw file. When I double clicked the raw file to open Photoshop I had the problem. I closed Photoshop and re-opened and imported the file instead of double clicking and all went smoothly. (though I've had the same problem with photoshop files and opening from within Photoshop doesn't always work).... Perplexing.
thank you for any help! sorry for my capitalizations.