Downloaded textures taking a while to display

You can see my system specs in my sig(System 2).
The default FS planes are fine, but alot of downloaded aircraft(mainly iFDG planes) textues take a few seconds to display in spot mode...it's just a black shell that comes up.
I've tried changing most things, I completely turned AA off but it made no difference, then I've lowered all the settings but still no help.
I've got a decent enough PC, any reason why or do you know what specific settings I should change?
Cheers.
The default FS planes are fine, but alot of downloaded aircraft(mainly iFDG planes) textues take a few seconds to display in spot mode...it's just a black shell that comes up.
I've tried changing most things, I completely turned AA off but it made no difference, then I've lowered all the settings but still no help.
I've got a decent enough PC, any reason why or do you know what specific settings I should change?

Cheers.