No $DISPLAY variable set over ssh

[allan <wizard10000@gmail.com>]

Have four Sid machines here and ssh -X has worked fine on all of them
for years. For the last several days I haven't been able to run
graphical applications over ssh from any of these machines.

Error says "cannot open display" and if I ssh into the machine
$DISPLAY is indeed blank but from a local console $DISPLAY correctly
reads :0

export DISPLAY=ip.of.ssh.guest:0 doesn't work either although it does
set the variable on the host machine. xhost + also gives the cannot
open display error.

ssh -vv -Y user@ip.add.re.ss just gives "X11 forwarding request failed
on channel 0"

Since this happened on all four machines at once I'm pretty sure it's
nothing I did - but I haven't been able to resolve it yet.

Anybody else seeing this? Anybody got an idea how to resolve or which
package to give a bug report?

cheers -