I've created a custom Preflight Profile that checks a PDF for any image masks. After selecting 'Masks' for the custom profile, I clicked on 'Custom checks' and scrolled about halfway down the list to select 'Image Masks'. I then added that to the list of 'Custom checks in this profile'. I then clicked on the 'Edit Checks' button at the bottom, and here is where the problems began.
I then selected 'Image' from the Group list and began adding various Properties from the subsequent list on the right. Although the new Properties showed up below, the OK button is constantly grayed out - I can only click CANCEL. Does anybody know what I'm doing wrong?