Parts of planes transparant

[Stiboo]

Help please !

Like most of us i'm tinkering with graphics setting all the time to get the right balance of quality and FPS...

I've got the sim running very well except for one annoying little thing which is parts of the plane are transparent - the propellor boss shows throught the spinner and parts of the cockipit can be seen through the body of the plane - also clouds in distance are in front of plane when u move camera?

This is in cockpit view and outside view...

Any thoughts / suggestions / cure !

Cheers

Simon