rsync - Apr 2002 - rsync 2.5.5 - "error in rsync protocol data stream"

I upgraded rsync from 2.3.1 to 2.5.5, and now one of my nightly
jobs fails with

    building file list ... done
    rsync: connection unexpectedly closed (11980581 bytes read so far)
    rsync error: error in rsync protocol data stream (code 12) at io.c(150)
    rsync: connection unexpectedly closed (8 bytes read so far)
    rsync error: error in rsync protocol data stream (code 12) at io.c(150)

I probably just need suggestions on how to better diagnose this,
but maybe someone can actually tell me what's going on here.

Here's what seems relevant:

The transfer only fails for certain large directories -- however,
there are no complaints of running out of space on the destination
host. (A test, where I invoked rsync separately for each subdirectory,
generated no errors -- does rsync need a certain amount of free disk
for some temp file, which grows with the size of the source data?)

rsync 2.5.5 (compiled from source with SUNWspro-5.0, on the same
machine which is running the rsync)
    hindenburg# /opt/rsync-2.5.5/bin/rsync --version
    rsync  version 2.5.5  protocol version 26
    Copyright (C) 1996-2002 by Andrew Tridgell and others
    <http://rsync.samba.org/>
    Capabilities: 32-bit files, socketpairs, hard links, symlinks, batchfiles, 
	          no IPv6, 32-bit system inums, 64-bit internal inums

Both hosts run Solaris 2.5.1

The transfer invoked as
	/opt/rsync-2.5.5/bin/rsync -azvH \
	--rsync-path=/opt/rsync-2.5.5/bin/rsync \
	--delete \
	/export/disk01/packages/ lusitania:/export/disk01/packages/

The source partition is

    /dev/md/dsk/d0       16489088 14390650 1603768    90%    /export/disk01

the destination is

    /dev/md/dsk/d0       16492328 14391420  451678    97%    /export/disk01

so, there isn't as much space on the targe as the source, but I
don't *think* there's anywhere near 451678 KB of updates.

Thanks, as always, for any clues!

David Harnick-Shapiro
<david@ics.uci.edu>