New Post: SPCascadingDropdowns() - Problem with Child Column of type Multi-Select-Hybrid

Yes, I did have to put it in 2013.01 as well. I pasted in exactly what ptavares had in the first comment (Including his comments).

I tried jquery.SPServices-2013.02BETA3 and unfortunately it exhibits the same concern.

                case "M":
    MultiLookupPickerdata.attr("value", newMultiLookupPickerdata);
    // Clear any prior selections that are no longer valid
    $(currentSelection).find("option").each(function() {
        var thisSelected = $(this);
        $(this).attr("selected", "selected");
        $(childSelect.Obj).find("option").each(function() {
            if($(this).html() === thisSelected.html()) {
                thisSelected.attr("selected", "");
            }
        });
    });
    // PT: Moved the setting of master.data here (from linke 1655)
    //     because:
    //     GipRemoveSelectedItems() (below on line 1653) calls
    //          GipSelectCandidateItems() who calls
    //              GipSelectCandidateItems() whow then calls
    //                  GipDisplayDescription() which attempts to
    //     use master.data[] and throws exception (line 380 of SP's
    //     groupeditempicker.js. 
    master.data = GipGetGroupData(newMultiLookupPickerdata);
    GipRemoveSelectedItems(master);
    // Hide any options in the candidate list which are already selected
    $(childSelect.Obj).find("option").each(function() {
        var thisSelected = $(this);
        $(currentSelection).find("option").each(function() {
            if($(this).html() === thisSelected.html()) {
                thisSelected.remove();
            }
        });
    });
    GipAddSelectedItems(master);
    // Set master.data to the newly allowable values
    // PT: Commented out code below and moved it above, to line 1641.
//                        master.data = GipGetGroupData(newMultiLookupPickerdata);

    // Trigger a dblclick so that the child will be cascaded if it is a multiselect.
    childSelect.Obj.trigger("dblclick");

    break;