This was kinda addressed in one of the NULL POINTER EXCEPTION error threads, but I would like to know the actual issue here, as we are having trouble with it in one of our projects. The guys that seem to have come up with an answer/solution are (not yet) registered on the Developer pages.... The issue Datamodel - Object - MEETING, has -1 relations with ATTENDEES - (ORGANIZER - the appointed official to lead the meeting) Object - MEETING, has *- relations with ATTENDEES Object - MEETING, has - relations with DISCUSSIONSUBJECTS Object - MEETING, has *-* relations with ACTIONPOINTS Object - MEETING, has 1-* relations with DOCUMENTS (to be clear, there are multiple DOCUMENTS associated with the MEETING. Form - base-datagrid = MEETING : selecting an ORGANIZER has an on-change to also add him as an attending member a Tab-container has 4 tabs, three tab host a referencesetselector to associated ATTENDEES, DISCUSSIONSUBJECTS and ACTIONPOINTS. The fourth has a datagrid to allowing use to see (and attach) he DOCUMENTS. the PROBLEM when I am preparing a meeting, allocating ATTENDEES and DISCUSSION_SUBJECTS and attaching DOCUMENTS I end up popping errors in the APP, console/log messages show it to be the NULL-POINTER EXCEPTION and the stack-trace show xpath and sort-order lines, which seem to imply this is related to the referencesetselectors The problem does NOT occur when opening the screen, but is pretty consistent when "refreshing" it after coming back to it "in content" Not using the Tab-container does not make a difference Suggestions anyone?