Are they still showing in sim as bmps? I just opened one with dxtbmp and it changed to bmp automaticaly. It might be a case of when they were first created they were named A273_.0af instead of A273_.bmp. If they're not showing after editing it might be because when saved they drop the .0af extension so have a look and if so rename them exactly as they were.
They don't show up as Bitmaps in the sim and renaming them Doesn't seem to have any effect. alterations I make don't seem to show up after editing I've tried using DXT Bmp, ConvR8, texture converters and they just will not let me edit the textures and save it back as a .af??? I dunno if it would have anything to do with it being an old alphasim payware model tre bizzare!!!