X Forwarding problems since upgrading to 6-Stable

[Tom Russo]

I have three BSD machines running 6-Stable, all of them only recently upgraded
from 5-STABLE.

Ever since the upgrades, I cannot get remote hosts to which I've ssh'd to 
connect to the tunneled X server.  For example:

  hostb> ssh -X hostA
  hosta> echo $DISPLAY
  localhost:10.0
  hosta> xev 
  Xlib: connection to "localhost:10.0" refused by server
  Xlib: Invalid MIT-MAGIC-COOKIE-1 key
  xev:  unable to open display 'localhost:10.0'
  hosta> exit
  hostb> ssh -Y hostA
  hosta> echo $DISPLAY
  localhost:10.0
  hosta> xev 
  Xlib: connection to "localhost:10.0" refused by server
  Xlib: Invalid MIT-MAGIC-COOKIE-1 key
  xev:  unable to open display 'localhost:10.0'

If hosta is not a FreeBSD machine, the *OPPOSITE* attempt works fine.  For
example, if hosta is my linux laptop:

  hosta> ssh -X hostb
  hostb> echo $$DISPLAY
  localhost:10.0
  hostb> xev
  [... xev starts up just fine and displays on the laptop...]

But if the machine from which I'm sshing is one of my 6-stable BSD machines,
it never works.  All the 6-stable machines are running the latest ports, as
I keep my ports tree csup'd and portupgrade regularly.  
 
I've googled the issue and the only thing I ever find is people answering
"you should use -Y instead of -X to enable 'trusted' forwarding."  This
clearly doesn't work for me, either.

Since I am not seeing tons of recent references to this all over the net,
I am pretty much concluding that I must have some kind of configuration 
mistake on my BSD machines' X or ssh setups, but I don't immediately see
one.  I thought I left my sshd config pretty much as it was out of the box, 
but perhaps I screwed something up.  Can anyone suggest a place to start looking
for the error?

-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236 AHTB#1 http://kevan.org/brain.cgi?DDTNM
"And, isn't sanity really just a one-trick pony anyway? I mean all you get is
 one trick, rational thinking, but when you're good and crazy, oooh, oooh,
 oooh, the sky is the limit!"  --- The Tick