Here is a workaround, save the MacInTax file to a floppy disk instead of the hard disk. You can then copy the MacInTax file in the Finder from the floppy disk to the UNIX hard disk.
It appears that MacInTax has a problem creating the file on the hard drive but not a floppy disk. Once the file has been dragged to the hard disk, MacInTax can open and update it without difficulty.
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