There are some files in my system which Dolphin informs me have MIME type "Empty Document"

The files are not empty, and it causes Dolphin to not display all the relevant information about the file (e.g. I have a jpg file without width and height info). Any idea how to debug this? Using KDE 4.12.3. Many thanks!

Can you please provide the output of "file --mime-type" when run against one of these files?
Also, can you check the permissions of the files to verify that your user is able to read them?

Output gives the correct MIME type. While I have no idea what was the problem, cutting and pasting the files to a different directory and then back into the same directory appears to have fixed it (i.e. it displays the correct MIME type as opposed to empty document). I do not know what caused the problem and I apologize that it did not occur to me to do the cut and paste before. I did it for the few files I had showing MIME type: Empty Document and now they are all correct.

Thanks for your help!

No problem. It is rather unusual that moving the files fixed the issue though, as mimetype determination is not cached by the system.