X11 auth data does not match fake data

Hi,

I am running OpenSSH version 5.3p1 on a Solaris 10 box.

I run X client "X1', say, with X11 Forwarding as user U1. Then I click
on a button in X1 which kicks off an ssh to a different user U2 and
runs a different X client X2.
X client X2 does NOT startup.

The error message is as follows:

debug2: X11 auth data does not match fake data.
X11 connection rejected because of wrong authentication.
debug2: X11 rejected 4 i0/o0

Ideas?
Any help would be appreciated.

Thanks,
Jon