6.0-RC1, X11 cut/paste between windows on different machines??!?

I finally(!) decided to go ahead & try RC1 even though my build machine
hasn't been working, so I built it on the 3rd bootable slice of my
laptop.

I'm using it now (while updating it to sources as of a couple of hours
ago).  It's mostly pretty good, but there is one thing that's nearly
driving me to distraction.

As mentioned, this is my laptop.  Now, my normal mode of interaction
with various machines is for me to fire up my laptop, then use SSH to
access all of the other machines with which I do anything.  (Save, of
course, when some interaction, such as pressing the "power" button on a
machine requires a more direct form of interaction.)

And in particular, on of the things I do moderately early in the AM (I'm
8 time zones west of UTC/GMT geographically), as I update the laptop, is
to don my postmaster_at_freebsd.org hat and start wading through the
messages -- the vast bulk of which are spam -- that have accumulated as
"held for moderation" in the various FreeBSD.org mailing lists.

And rather than merely discard all of the spam, I check it (via a
comobination of scripts & manual inspection) so I can update the
anti-spam filters both on my home MTA and the one for BayLISA.

I have become accustomed to being able to use cut/paste rather freely
from any text window running on one machine to any text window running
on any machine.

That has worked while running FreeBSD 4-STABLE and 5-STABLE on the
laptop, but is working only sometimes (and I've yet to discern the
pattern) while running FreeBSD 6-RC1 on my laptop.

Now, I've not changed anything with respect to ACLs, PAM, or much of
anything.  And I never did spend a huge amount of time running 5.x;
I still use 4-STABLE for day-to-day work.

I use xdm to create the X11 environment, in case that has some relevance.
And I use "piewm" (a variant of tvtwm) as a window manager.

My home directory (on the laptop) -- and thus, my ~/.xsession file, in
particular -- is shared among the various versions of FreeBSD that I
run on the machine.

Symptoms...  Sometimes (as mentioned above), the cut/paste works
fine.  Sometimes it doesn't.  And in the latter case, what gets
pasted into the target window is whatever had last been "cut" on
the machine where the target window is running.  And -- as an added
feature, I suppose -- it seems to be the norm (in the "non-working"
case) for the source window to be closed (and the process that had
been running it to die).

So I typically am trying (during the above-described scenario) to use
cut/paste among the following machines:

* my laptop
* freefall
* hub
* baylisa
* my internal mail server (at home)
* my external mail server (at home)

I use ssh to access each of them -- most directly from my laptop; the
exception is my external mail server:  to get to it, I use ssh to login
to my internal mail server first; from that machine, I can login to the
external mail server (also via ssh).

An attempt to run "xclipboard" on my laptop, type something there, then
use cut/paste to paste what I typed there into a window running on my
internal mail server caused the xclipboard process on my laptop to die.

Running xclipboard on the internal mail server itself (but displaying it
-- like everything else under discussion -- on my laptop) avoided that
mode of failure.

But then, trying to cut/paste from that xclipboard to the baylisa
machine killed off xclipboard.

On the other hand, cut/paste from the internal mail machine to freefall
worked fine.

Trying to cut/paste from freefall to the baylisa machine killed the
freefall window's process.

Trying to cut/paste from my external mail server to the baylisa machine
killed the process on the external mail server.

OK; that's not all of the combinations; I doubt that more than 2 or 3
folks have read this far, and I don't want to bore to many folks to
death.  But perhaps there's enough of a pattern that someone more
familiar with what is likely to have happened to be able to provide me a
clue, ask some salient questions, or suggest some experiments.

I'll summarize off-list responses.

Thanks.

Peace,
david
-- 
David H. Wolfskill				david_at_catwhisker.org
Prediction is difficult, especially if it involves the future. -- Niels Bohr

See http://www.catwhisker.org/~david/publickey.gpg for public key.