I posted on fedoraforum.org and got a workaround for the xchat-gnome bug.
1. run gconf-editor (yum install gconf-editor)2. go to apps->xchat->main_window3. set "background_transparency" to 04. You should be able to use xchat-gnome as you did before
Its a reported bug : https://bugzilla.redhat.com/show_bug.cgi?id=478649
I used the workaround to reporoduce it.. :)