Comment 91 for bug 1432194

I was able to resolve this on trusty doing the following:

sudo apt-get install xserver-xorg xserver-xorg-video-intel (and all the depends)

then reboot.

Just FYI, i'm on -30 kernel, and using ubuntu-mate as as desktop.

Linux dave-ot-trusty 3.16.0-30-generic #40~14.04.1-Ubuntu SMP Thu Jan 15 17:43:14 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

~ % dpkg -l xserver-xorg
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==============-============-============-=================================
ii xserver-xorg 1:7.7+1ubunt amd64 X.Org X server

~ % dpkg -l xserver-xorg-video-intel
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==============-============-============-=================================
ii xserver-xorg-v 2:2.99.910-0 amd64 X.Org X server -- Intel i8xx, i9x

~ % dpkg -l ubuntu-mate-desktop
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==============-============-============-=================================
ii ubuntu-mate-de 1.119~trusty amd64 Ubuntu MATE - full desktop

No more issues with missing characters, unstable graphics, etc.