I'm running Ubuntu 14.10 in VirtualBox under OSX and for some reason pasting with the middle mouse button stops working after a while. If I start a new rxvt pasting works fine but after a while (I'm unsure how long) pasting with the middle mouse button no longer works (in any program).
I can see with xsel that the text is copied and I can see with xev that X receives "button 2" when I press the button (which is actually remapped to Command_R in OSX). When I start a new rxvt-instance then pasting starts to work again (for a while) in all open rxvt-windows. Starting an xterm also gets it to work again, but starting xclock does not. So it seems like someone removes the paste function from the button 2 event, and that it is re-added when a terminal is started.
Any ideas on how to debug this?