OclSobelFilter: image problem

I’m playing with the nvidia sdk, I’m triying to run OclSobelFilter on other image that the one used by default
when I try with lenaRGB.ppm for example, it doesn’t work, and I got :
sobel.exe: Native’ has exited with code 1 (0x1)
is there something you have to do to suit the code to any image.