iraf.net

Dear Sir/Madam,
My name is Gareth Power. I am a Master's student at U.C.C. in Ireland
and my research involves the application of optimum aperture photometry
to radioquiet quasars. I am having problems using the zerocombine and flat-
combine commands, which invariably give an error message along the lines of
error in line 46: no frames to combine, in spite of the fact that the
frames in question have been specified in the parameter list, and can readily
be displayed. Occasionally, the message error in line 46: segmentation
violation appears in place of the above. Can this be a problem with the
way IRAF has been set up in my account. Another student performing the
same kind of work on the same computers here - Pat Doyle - has no such
difficulties. In his account, flatcombine and zerocombine work properly.
We haven't been able to find any differences in the way IRAF has been set
up in the two accounts, but perhaps something subtle is there.
I would appreciate any help you can provide.