I published an InfoPath form on my SharePoint which contains a multiple selection list box. The Problem is that when i try to edit an item in line every value except for the "allow-users-to-enter-custom-values"-box are shown. Why isn't the last one visible?
If your InfoPath is connected to a SharePoint List, it is also connected (most-likely) to a Choice List (multi-choice). On that column, you need to ensure that "Allow Custom Values" (on the Column in the SharePoint list settings) is checked.