package failed

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hi.
i have a problem. no matter whitch packeges i try to install on fedora core 4 i get the same error.
the error is:

Reading system installed packages...done.
Download file plesk-8.0.0-fc4-i386.hdr.gz: 73%..100% done
Download file plesk-8.0.0-fc4-i386.hdr.gz: 38%..97%..100% done
Resolve components
ERROR: Can't add to black list product package psa-proftpd
ERROR: Installation failed


what can i do?