==How can I know more about Octave GUI?==
This is being developed as part of the Octave project so subscribe to the [http://www.gnu.org/software/octave/get-involved.html maintainers mailing list]. When you checkout the Octave repository, you'll find the GUI source on the development/default [http://hg.savannah.gnu.org/hgweb/octave/branches branch].
==I'm having problem XXX using GUI Octave, XOctave, QtOctave, etc?==
Install Octave only, without any of the non-supported by GUIs and see if the problem disappears.