Problem with pg_restore

PostgreSQL version 8.1.4
Linux version 2.6.19-gentoo-r5 (gcc version 4.1.1 (Gentoo 4.1.1))

I make backup with commang:
pg_dump  -U postgres -h /tmp -Ft -b -C mydb > file.tar

When I want to restore from backup, i give error.

pg_restore -U postgres -d template1 -v -C < file.tar

error report:
    Command was: COPY sl_log_2 (log_origin, log_xid, log_tableid, log_actionseq, log_cmdtype, log_cmddata) FROM stdin;
pg_restore: [tar archiver] corrupt tar header found in 119 (expected 100, computed 40443) file position 4296575488
pg_restore: *** aborted because of error