Accessviolation Ecxeption in MeanShift Segmentation code

Accessviolation Ecxeption in MeanShift Segmentation code

I wote this code for segmentation with mean-shift:
var sourceImage = new GpuImage<Bgra, byte>(new Image<Bgr,
byte>("books.jpg").Convert<Bgra, byte>());
var targetImage = new Image<Bgra, byte>(sourceImage.Size);
GpuInvoke.MeanShiftSegmentation(sourceImage.Ptr, targetImage.Ptr, 20, 30,
3, new MCvTermCriteria(5, 1));
My Graphic card is a NVIDIA Quadro NVS 140M and the drivers are current.
But, when I run the code, an AccessViolation exception occurs.
Can anybody tell me why this exception occurs? and how can I solve it?