Comment 2 for bug 1376300

I had the same issue on a fresh install of 16.04, after installing the brother drivers with their automatic script.

I ran an strace of simple-scan, as recommended by Kuwanger in the IRC, and found that simple-scan didn't have permission to access some cache files.

The problem was that simple-scan's cache files were owned by root, and not accessible by the user. The solution was to run

sudo chown -R <yourusername> ~/.cache/simple-scan

Of course, replace <yourusername> with the name of your user. I hope that helps!