Can anyone help?

I keep downloading aircraft, but after installing, keep getting a message saying it cannot visualise the flight mode. in the little preview window. If I click okay, I get an invisible aircraft on the runway. This only happens with the more detailed aircraft I download. If I get the really basic ones, it works.

I have a pretty good graphics card and my computer is not that slow. Does any one know whether it has something to do with graphics settings or anything??

Any help appreciated. Thanks.