opencv highgui error [closed]

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Hi
I wrote a ros node that takes a video from a webcam and publish its frame and it works.
Yesterday I installed the driver for video capture "media_build" to take a video from a video grabber, but the same program doesn't work, while if I open "video for linux 2" on VLC it works.

This is the error:

libv4l2: error set_fmt gave us a different result then try_fmt! HIGHGUI ERROR: libv4l unable convert to requested pixfmt
HIGHGUI ERROR: V4L: device /dev/video0: Unable to query number of channels
ERROR: capture is NULL

The instruction is:

CvCapture* capture = cvCaptureFromCAM( CV_CAP_ANY );
if ( !capture ) {
fprintf( stderr, "ERROR: capture is NULL \n" );
getchar();
return -1;
}

any suggestion? (P.S. I have ros fuerte in my ubuntu pc)
thanks