cannot copy/pate between LyX and other application

[Ramin H]

Info: Gnome Desktop, RedHat 9, LyX 1.3.1

I can copy/paste between LyX documents within LyX. I am also able to
copy/pate between different text editing applications in my Gnome
environment.
But,
I am not able to copy/paste simple text between LyX and other text
editing applications in my Linux environment.

Any suggestions regarding how to solve this problem?

Thanks.
-Ramin