Why SSH X forwarding opens application in text mode ?

Issue

• Start first ssh session using ssh -X from client to RHEL6 system, gets display variable as localhost:10.0 this opens up a GUI application (emacs) it opens fine, logout using <CTRL>+<D>

• Open a second ssh -X session from client to RHEL6 system, gets display variable as localhost:10.0 now GUI application fails to launch, if tries to open emacs it opens in a text mode.