I've read the forum and seen this problem repeated in the past, and I did not see a simple, permanent fix resolution from wordpress admin.
I've been uploading images into posts without a hitch until this evening. Have always used the "medium" 300x300 setting before, all of a sudden thumbnail and all sizes are grayed out radial buttons, except for Full-Size which is defaulted.
What happened? It is not the theme, already tried that. It might be the build, as a blog still running on 2.7 or whatever old version does not have this problem
please help ASAP!!!