Installed the configuration slicing plugin and tried to change my "Ant version per Project".
I've putting some project from "Default" to "Ant 1.9.4" and "Saving" the page - but after looking back at the configuration nothing have changed.
In contrast i've tried it with "JDK per project" - that worked - but not for Ant.
There is no error message on the page, neither in the logs when trying to change the Ant configuration.