Acorn 6 was recently released, and it exposed a subtle bug in our Acorn Plugins that caused it to load the images with a reduced bit depth. With help of Acorn’s developer we have resolved the issue, and the updated plugins are now available.
The images loaded just fine on Acorn 5.6.5, but the update is also recommended for users of this version.
More information about these plugins and the download link can be found in the User Guide. Full release notes are here.