This is Debian bug 345700. Adding option XaaNoSolidFillRect to the top of your Screen section of your xorg.conf works around it, like this:
Section "Screen" # Workaround for Debian bug 345700, Ubuntu bug 77774 Option "XaaNoSolidFillRect" ... Added link to the Debian bug. ** Bug watch added: Debian Bug tracker #345700 http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=345700 ** Also affects: xserver-xorg-video-nv (Debian) via http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=345700 Importance: Unknown Status: Unknown -- Text cursor appears in wrong place(s) https://launchpad.net/bugs/77774 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs