Quicktime supports only files with 3/4-channels rgba-files and not 1/2-channels rgb-files.
This submission is from Tatsuhiro Nishioka, here's his original quote:
When FlightGear crashes, the error message
"GraphicsImportGetNaturalBounds failed" shows up. By adding printf
debug, I found the error was -8969: codecBadDataErr when loading a
gray-scaled (2 channels) rgba files even though the file can be loaded
with Gimp and osgViewer properly.
So I made an investigation on this problem and found an interesting
thing. This error occurs only when non-rgb files are loaded before rgb
files. The reason is that rgba files can be handled by both
osgdb_rgb.so and osgdb_qt.so, but the error happens only when
osgdb_qt.so try to load a gray-scaled rgba file.
When a program is about to load an rgba file, osgdb_rgb.so is loaded
and it handles the rgba file properly. In contrast, when a gray-scaled
rgb file is being loaded after a non-rgb file (say png) is already
loaded by osgdb_qt.so, osgdb_qt.so tries to load the file instead of
osgdb_rgb, which causes the error above.
Anyway, the bad thing is that QuickTime cannot handle gray-scaled rgb
files properly. The solution for this is not to let osgdb_qt handle
rgb files since osgdb_rgb can handle these properly.
"