Pasting into terminal works on and off

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http://ubuntuforums.org – Ubuntu 12.04LTS. After working flawlessly the terminal pasting functionality turned erratic at some point which I can't relate to any preceding occurrence. I spent a few hours scouring this forum and found relevant comments and suggestions, but nothing conclusive. I also mention, whether or not it matters, that quite some time before the problem started, I had gotten rid of malfunctions that seemed related to compiz (being no longer supported?). Following a related thread on this forum I downgraded with "apt-get install gnome-session-fallback". The downgrade may have introduced confu (Hardware)