I have long had troubles with that file.  In my case, I use a chain of
a junkbuster (to work around firewalls), an on-machine squid, zero or
one intermediate squids, and a final junkbuster (to block ads).
I use this for both http and ftp.
The distfile is normally over ftp, and I find that fetching it over
http gets it wrong (crlf issues, and I forget the details).  I suspect
that the file has crlf in it and is normally fetched in binary mode,
but that the http proxy translates it to/from wrong, but I never
figured it out.

Your problem is different, but may have the same underlying crlf
confusion.

-- 
        Greg Troxel <gdt@ir.bbn.com>