rsync and plink (putty) fails, but cygwin ssh works

[bwooster47]

I've got this working with the Cygwin rsync and Cygwin ssh - Windows
is client machine, sending data to a Linux box. Not using rsyncd on
linux, just using SSH.

So, this command, using all Cygwin commands, works fine from Windows
XP box:
c:\cygwin\bin\rsync.exe -avz -e "c:\cygwin\bin\ssh -i /cygdrive/c/
myssh.key" /cygdrive/c/home/ user@remote:/backup

Similarly, one would assume plink would work - this is from the Putty
package, but it fails with
...
opening connection using plink -v -i "\myssh.ppk" -l user remote rsync
--server -vlogDtprz . /backup
...
Started a shell/command
Unable to read from standard input: The handle is invalid. [*** this
is the failure **]
rsync: read error: Connection reset by peer (104)
rsync error: error in rsync protocol data stream (code 12) at /home/
lapo/packaging/tmp/rsync-2.6.9/io.c(604) [sender=2.6.9]

Full command was something like:
\cygwin\bin\rsync.exe -avz -e "plink -v -i \myssh.ppk" /cygdrive/c/
home/ user@remote:/backup

Just plink works fine:
plink -i \myssh.ppk -l user remote echo AAA
AAA

So, is this problem in the way rsync opens up the filter (looking for
stdin), or something that plink is not doing right, or something
related to Microsoft Windows?