iraf.net

Hi,I've been trying to analyze data using the mscred package. Even though the images are obtained with one CCD, the readout is performed by 4 amplifiers and images are written as 4 extensions into a fits file. So mscred package is being used.After combining my zero and flat field images using the zerocombine, flatcombine and the ccdproc tasks. When I try to obtain these to a new image i get the following error message :mscred> ccdproc
List of Mosaic CCD images to process (object0056.fits):
ERROR: CCD sum error: target='-1 1', calibration='1 1'
"low_reject=low_reject, high_reject=high_reject, grow=grow)"
line 286: mscsrc$ccdproc.cl
called as: `ccdproc ()'When combining the zero and flat fields I do apply the overscan and trim corrections. I also merge the images.I was wondering what may be wrong to cause this error message, because just a couple months ago with the same IRAF, I was able to calibrate the images I obtained from the same detector with the same format. So I suppose it is probably a configuration problem.thank you very much for your suggestions,
tolga