If you are suffering from random letters dropping off your screen then a short post here on how to workaround this.
This particular annoyance occurs for me after a few minutes of boot up – especially if waking up from being suspended.
I’m using Intel graphics – vivid (15.04) HWE on Ubuntu 14.04. This occurred also when I was using utopic (14.10) HWE.
sudo nano /etc/X11/xorg.conf
copy and paste (CTRL + INS) the following
Identifier "Intel Graphics"
Option "AccelMethod" "uxa"
CTRL+X and answer yes to save and exit. Finally reboot.
If this happens for you – click the “this affects me” option on this bug-report.
So what does this do? Well, it tells the Intel graphics driver not to use the default SNA code path but instead use the older UXA code-path. The older code-path is a kind of fall-back and isn’t as efficient as the newer SNA graphics.
To go back to the newer graphics either remove the xorg.conf file you created above – or just rename it followed by a reboot i.e.
sudo rm /etc/X11/xorg.conf
sudo mv /etc/X11/xorg.conf /etc/X11/xorg.conf.backup
N.B. I’ve seen other suggested workarounds such as tweaking the DPI settings and antialiasing changes but these do not work for me 😦