Now you might be asking, why would some obscure ESRI extension supporting 9.3.1 be news? Well if you work with NITF data, it is important to you. Plus you are probably on a government computer and ArcGIS 10 is a distant dream.
Anyway NITF for ArcGIS now support 9.3.1 so if you are rolling with ArcGIS 9.3.1, you can now work with NITF again. Hold the line guys!