Well MOST 3rd party software are NOT compatible with DX10.
Having texture woes is 100% guaranteed if you load up a flight with an aircraft that is not DX10 compatible.
This is not limited to 3rd party aircraft but also the case with scenery/texture add-ons.
If they are not DX10 compatible then this will happen.
Have you tried this in DX9 mode and see if the problem persists?
Also check your sliders, reduce graphic options, FSX is CPU mad and might battle to display textures if settings are too high.
Goodluck :)
PS: If non-of-the-above works I suggest you phone Ghost Busters as you might have a poltergeist in your rig ;D

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