Imagemagick thumbnail not working with NextGEN Gallery plugin

I’m using NextGEN Gallery (nggallery) plugin v 1.8.3 by Alex Rabe

I’m getting poor quality thumbnails generating on my site so I want to use ImageMagick instead but when I check that option in the options tab under gallery tab the thumbnails go through the orange bar generation process but do not appear at the end of it. Instead I get a blank box with a line around it.

Myhost support team have recreated the issue but cannot resolve it as no error message gets created – help!

I also operate Highslide for WordPress “reloaded” v1.2.2. So unsure which of the two plugins are generating the thumbnails