This is the full description from the Squid changelog. An
update to 2.2.STABLE3 should thus fix the problem.
ftp.pc.ibm.com is rather important, since IBM uses it to
publish updates.

Broken FTP server's return SIZE 0

     Version: 2.2.STABLE2

     Platforms: All

     Reported by: Markus Leutwyler (markus.leutwyler at
inserto dot ch)

     Synopsis: IBM's FTP server (ftp.pc.ibm.com) returns
``213 0'' in response to a SIZE command, even though the
file has non-zero size. Squid puts
     ``Content-length: 0'' in the reply header.

     Patch: ftp.c-zero-size.patch

     Status: Fixed in 2.2.STABLE3