After highlighting text at the command line in Gnome-Terminal with my mouse and then either (1) right-clicking to copy and paste or (2) center-clicking to paste, nothing has been copied. I can copy fine in windows of any other Linux application and paste that material into the command line, but if I try to then copy and paste something from the command window, only the most recent non-command-window text that I copied will be pasted.
Try highlighting text in gnome-terminal and pressing ctrl+shift+c to copy it. Similarly, pressing ctrl+shift+v should paste text into gnome-terminal.
The idea is that we need the shift key too because at the command line, ctrl+c is used to abort the currently running process.