FLEX-33272. RTE occurred while trying to hide columns of an AdvancedDataGrid having lockedColumnCount greater than 0 that was scrolled all the way over to the right. When the columns were hidden the horizontalScrollPosition was no longer valid and visibleColumns got out of sync with the newly updated displayableColumns.
incubator/flex/sdk/branches/develop/frameworks/projects/advancedgrids/src/mx/controls/AdvancedDataGridBaseEx.as