Disappearing helicopters?

[Howser]

What's up with these disappearing helicopters? They are the only vehicle that shows this behaviour; http://www.youtube.com/p.swf?v....BFF9unk (http://www.youtube.com/p.swf?video_id=af5aAlW42fM&eurl=&iurl=http%3A//sjl-static5.sjl.youtube.com/vi/af5aAlW42fM/2.jpg&t=OEgsToPDskLz4tuZ25xIUw3AXBFF9unk)

P4 3.0 / 1536 MB RAM / 7600GT / WinXP Pro

German 1.01 version of ArmA with English language patch applied.

Everything updated.