I think either Shessi or Gaucho has the answer.
The paint shows up on the aircraft selection list, so the title line must be OK (it doesn't matter what that line says, as long as it's not the same as that line in another UI section.) So if the problem is in the aircraft.cfg file, it must be that the texture= line or the folder name.
If you made no modifications of any kind to the textures, then it would almost have to be that the paint's folder name doesn't match the name in the title= line of the cfg file. Or perhaps a typo inserted a comma instead of a period between texture and the paint name, so it reads texture,paint instead of texture.paint. Look for any misspellings in either the texture= line or the texture folder name.
If you're sure that the cfg file is OK, then the problem is probably the texture files themselves. Is it possible that you inadvertently changed them? AS Gaucho mentioned, while FS9 reads panel backgrounds in 24-bit format, it can not read external texture files in that format. Textures have to be in 256 colors, 32-bit, DXT-1 or DXT-3 format.
There's not much chance of turning a 256-color file into something else by accident, since fiddling with it in a graphics program won't change the format unless you tell it to. And, it's hard to imagine anyone repainting a high quality payware plane like that in low-quality, fuzzy 256-color textures. It's not likely that you changed a DXT texture to something else by mistake because you couldn't even open it except in a specialized program like DXTbmp, and it would be unlikely (though maybe not impossible) to save it in a different format without doing so deliberately.
But 32-bit textures could be inadvertently changed into 24-bit format, and since you're dealing with a repaint for a high quality payware plane, I'm betting that the repaint is probably in high quality 32-bit format. You can open and view a 32-bit file in any image program, but you can't save it in 32-bit unless you're using DXTbmp (or some comparable program, is there are any.) If you make any change, no matter how tiny, your image program will automatically convert the file to 24-bit when it saves the changes. And FS can't read 24-bit files.
If you deliberately changed a 32-bit file in a regular imagery program and saved it, you accidentally converted it to 24-bit format, and there's the explanation for your problem.
If you just opened the file to look at it, and perhaps made just one tiny mouse click in the image window, that would change just one pixel's coloration, and if you inadvertently clicked "yes" when the program asked if it should save the changes, the file would save in 24-bit format.
Anyway, after way too much background explanation, here's my suggestion:
Delete the texture folder of the affected paint and replace it fresh from the zip file you downloaded. That might be all you have to do.
If that doesn't work, then try opening each external texture file in DXTbmp and check to make sure it's in a format that FS9 can read.
One more thought: are you sure this is an FS9 repaint? If it's an FSX paint it might be in a format that FS9 can't read, or the file sizes might be too big for FS9 to handle, or both. There is a way to convert FSX textures for use in FS9 but I don't know how to do it. If that's what needs to be done, I'm sure someone here can tell you how.
