NGX bounces up problem

Hello,

Since short i noticed a problem with the NGX + Saitek Pedals + ImagineSim VHHH

When the airplane starts to move and i press the pedals with my feet all of the sudden the aircraft jumps of to 500FT.

And it then flies off. 

So what happens is that the plane apperently falls down the scenery, the wheels fall through the tarmac textures, which makes the ngx thinks its flying. calling out V1, VR and V2 and so on.

This happens every single time I press the pedals. I can put the plane back at a position at the airport. does not matter where, it keeps occurring. I have this problem only with this addon of VHHH and this plane. 

Does anybody have know what i might need to change in order to get this working?

Kind regards,

Yori Smulders