This script still doesn't address the underlying problem of what is messing up those files, but it works.
#!/bin/sh
rm /sw/bin/{tar,gzip,gunzip}
ln -s /usr/bin/gzip /sw/bin/gzip
ln -s /usr/bin/gunzip /sw/bin/gunzip
ln -s /usr/bin/gnutar /sw/bin/tar
Regards,
Pedro
