Help with a shudder and vibration

[Simon_0106]

Hi,
Can anyone give me some ideas with a horrible shudder/vibration i am getting on my e53? It happens whilst I am doing apx 40mmph on a sweeping right hand bend only (steering wheel very slightly turning right) left seems ok. It feels like the wheel is going to fall off and entire steering wheel shakes very badly and cabin rattles to bits. I mean really bad - enough to make you crap yourself and stop.
I have fitted powerflex bushes all round (except anti roll bar and rear subframe bushes) but have fitted oem subframe bushes and anti roll bar bushes. I have replaced discs and pads and front link rods (oem again).
I have had wheels balanced to zero and 4 wheel alignment.
Has anyone got any ideas? ny help or pointers would be great.
Do drive shafts/propshafts fail often on x5's. this is a 2001 model 3.0d.
Thank you in advance.