Maybe I'm having a blonde moment and am forgetting a major step, but my thumbnails refuse to sharpen in my gallery : http://scarlett-gallery.com
I was able to get it to work fine on a test gallery : http://snappy-snippets.net/cpg148 So I'm confused as to why I'm having trouble now.
With screencaps it's hard to say...
1. Disable sharpening in config.
2. Upload a testpic (try a portrait).
3. Enable sharpening (standard settings).
4. Upload the same testpic again and compare.
5. In case try more aggresive settings and retry uploading the testpic.