This is because gnome-terminal now correctly delivers the right-click event to vim (or any application that is interested in mouse events). In 14.04 it was impossible for vim (or any other app) to receive right- clicks in gnome-terminal.
You might either disable mouse support in vim, or invoke the context menu with Shift + right-click, or use the top menu bar or the shortcut key Ctrl + Shift + C/V. ** Bug watch added: GNOME Bug Tracker #13299 https://bugzilla.gnome.org/show_bug.cgi?id=13299 -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to gnome-terminal in Ubuntu. https://bugs.launchpad.net/bugs/1610882 Title: No context menu in VIM in gnome-terminal after upgrade to xenial Status in gnome-terminal package in Ubuntu: New Bug description: After upgrade to 16.04, I am no longer able to copy / paste text from clipboard in VIM using gnome-terminal. The previous sequence of actions that worked on 14.04 was: to copy: 1) select text holding shift 2) right click using mouse 3) click "Copy". To paste: 1) In insert mode, right-click mouse 2) click "Paste". This issue does not exist in mate-terminal. ProblemType: Bug DistroRelease: Ubuntu 16.04 Package: gnome-terminal 3.18.3-1ubuntu1 ProcVersionSignature: Ubuntu 4.4.0-31.50-generic 4.4.13 Uname: Linux 4.4.0-31-generic i686 ApportVersion: 2.20.1-0ubuntu2.1 Architecture: i386 CurrentDesktop: Unity Date: Mon Aug 8 11:06:28 2016 InstallationDate: Installed on 2014-01-25 (926 days ago) InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release i386 (20131016.1) SourcePackage: gnome-terminal UpgradeStatus: Upgraded to xenial on 2016-08-04 (3 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-terminal/+bug/1610882/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp