pkg_add: Read error - Premature end of gzip compressed data: Input/output error

[Hubert Feyrer <hubert%feyrer.de@localhost>]

I've tried to install nethack-tty via pkg_add tonight, which pulls in 
nethack-lib. Halfways through, I got this error:

        # echo $PKG_PATH
        ftp://ftp.NetBSD.org/pub/pkgsrc/packages/NetBSD/i386/5.0/All
        # pkg_add -v nethack-tty
        ...
        share/nethackdir340/wizard3.lev
        share/nethackdir340/wizhelp
        Running install with PRE-INSTALL for nethack-lib-3.4.3nb2.
        nethack-lib-3.4.3nb2: /usr/pkg/share/nethackdir340/logfile already 
exists
        nethack-lib-3.4.3nb2: /usr/pkg/share/nethackdir340/record already exists
        Package nethack-lib-3.4.3nb2 registered in 
/var/db/pkg/nethack-lib-3.4.3nb2
        Running install with PRE-INSTALL for nethack-tty-3.4.3nb1.
===> pkg_add: Read error for bin/nethack-tty: Premature end of gzip compressed 
data: Input/output error
        bin/nethack-ttyoriginal MD5 checksum failed, not deleting:
        /usr/pkg/bin/nethack-tty
        pkg_add: 1 package addition failed

        # pi -e nethack\*
        nethack-lib-3.4.3nb2

Running the same pkg_add command again installed the program properly,
so this is most likely not caused by a broken binary package.
I've seen this before, and I onder if anyone has seen this, too, and maybe 
investigated what happened?

FWIW, this is on NetBSD 5.0/i386, pkg_add -V says "20091015".


 - Hubert