I have this one image that C1 simply refuses to work on (it displays fine). It's a grayscale step wedge TIFF file.
At first I thought C1 doesn't like the grayscale color profile, so I converted it to sRGB, no effect.
I then converted it to png, and jpg, still read-only.
Amazingly enough, if I take a screenshot of the screen displaying the image and crop to that image, it still refuses to edit it!
The file can be edited in Photoshop and Adobe Camera Raw without problems.
The file is read-write and has no extended attributes. The file can be found
here (21 step grayscale wedge).
What is going on?