How do you configure X11 forwarding over SSH on AIX?

Solution 1:

DISPLAY=localhost:10.0
export DISPLAY

I presume this is in your shell startup files (.bash_profile or similar)? Try removing it. ssh -X automatically sets this variable for sessions where it's forwarding X. It shouldn't be necessary for you to set this variable manually, and you may be setting it to the wrong value.

By way of background, the default TCP port for X is 6000, corresponding to "localhost:0.0". ssh -X normally starts with port 6010, which corresponds to "localhost:10.0", and works upwards until it finds a free port. If port 6010 was in use, then it might bind to 6011 and set DISPLAY to "localhost:11.0". This is why you should let ssh set DISPLAY for you.