X-forwarding Unbearably Slow, firefox on SIMpad unusable Options

[Master One]

I finally came around to test X-Forwarding on the SIMpad, as described here.

It kind of works, but it is unbearably slow. Connecting to an Ubuntu Hardy box with Firefox 3.0.1, this is what I get in the terminal:

CODE

$ssh user@ubuntubox -X firefox

(firefox:7819): Gdk-WARNING **: Connection to display localhost:10.0 appears to be untrusted. Pointer and keyboard grabs and inter-client communication may not work as expected.

(firefox:7819): Gdk-WARNING **: Coercing GDK_INPUT_ONLY toplevel window to GDK_INPUT_OUTPUT to work around bug in Xorg server

(firefox:7819): Gdk-WARNING **: Coercing GDK_INPUT_ONLY toplevel window to GDK_INPUT_OUTPUT to work around bug in Xorg server

(firefox:7819): Gdk-WARNING **: Coercing GDK_INPUT_ONLY toplevel window to GDK_INPUT_OUTPUT to work around bug in Xorg server

Firefox then starts, but it takes ages till the window display is completed, and then trying to use firefox on the SIMpad is that unbearably slow, that it can not be used seriously.

What can be the reason for that behaviour?
Does anybody have it working properly?
What about the shown two error messages?
Is it possible, that the SIMpad is not powerful enough, to handle such X-Forwarding over SSH on a WPA secured wireless connection?
Or is it possible, that this is some kind of networking problem (like OpenSSH trying to resolve the hostname or FQDN / DNS problem)?

[Master One]

CODE

$ DISPLAY=simpadip:0 firefox
No protocol specified
Error: cannot open display: simpadip:0

That's all I get, when trying SSHed into the Ubuntu-box. I do not really have any experience, when it comes down to X-Forwarding, so what could be the issue with this approach?

P.S. If the solution with X-Forwarding over SSH really is too demanding, why is it not mentioned in the HowTo on opensimpad.org under "Possible problems"? Since others seem to have it working properly, I am not convinced, that the problem I'm experiencing are a general issue.