Odd behaviour going on, but is reproducible on my system with the following steps. 1) open xfce4-terminal 2) ensure the window is big (mine was exhibited on 240x100 using Monospace 9 font) 3) run a long running command that will scroll output constantly through the terminal (eg ls / -R) 4) while the terminal is scrolling output, hit printscreen, which has been mapped in the xfce keyboard settings to run the command 'xfce4-screenshooter -w -c' 5) attempt to paste the screenshot into GIMP GIMP hangs for about 30 seconds, before popping up a dialog 'GIMP Message' 'There is no image data in the clipboard to paste' Hitting printscreen while the terminal is idle (not scrolling output) works just fine. xfce4-screenshooter 1.8.1 xfce4-terminal 0.6.3 (Xfce 4.10)
I think it's not related to terminal window, currently any large screenshot fails to be copied to clipboard, as discussed in #13342. Even though this bug is older, I'm going to close it as the discussion is more detailed in #13342. *** This bug has been marked as a duplicate of bug 13342 ***