package management - Error when trying to install, debconf resource temporarily unavailable

I'm trying to run webgl apps in my web browser but whenever I try to, nothing happens. I found that ubuntu-restricted-extras can be installed to enable webgl. One of my friends installed the package on their system and was able to run the webgl app that I was trying to run. When I tried to install the package using the Ubuntu software center, the download stalled so I had to kill the process.

Output of sudo apt-get install ubuntu-restricted-extras

Reading package lists... Done
Building dependency tree
Reading state information... Done
ubuntu-restricted-extras is already the newest version.
The following packages were automatically installed and are no longer required:
  python-cssselect python-queuelib python-w3lib
Use 'apt-get autoremove' to remove them.
The following packages will be upgraded:
  ttf-mscorefonts-installer
1 upgraded, 0 newly installed, 0 to remove and 145 not upgraded.
1 not fully installed or removed.
Need to get 0 B/27.8 kB of archives.
After this operation, 134 kB of additional disk space will be used.
debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable
(Reading database ... 286934 files and directories currently installed.)
Preparing to unpack .../ttf-mscorefonts-installer_3.4+nmu1ubuntu1_all.deb ...
debconf: DbDriver "config": /var/cache/debconf/config.dat is locked by another process: Resource temporarily unavailable
dpkg: error processing archive /var/cache/apt/archives/ttf-mscorefonts-installer_3.4+nmu1ubuntu1_all.deb (--unpack):
 subprocess new pre-installation script returned error exit status 1
Errors were encountered while processing:
 /var/cache/apt/archives/ttf-mscorefonts-installer_3.4+nmu1ubuntu1_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

Output of apt-cache policy ubuntu-restricted-extras

$ apt-cache policy ubuntu-restricted-extras
ubuntu-restricted-extras:
  Installed: 60.1
  Candidate: 60.1
  Version table:
 *** 60.1 0
        500 http://us.archive.ubuntu.com/ubuntu/ trusty-updates/multiverse amd64 Packages
        100 /var/lib/dpkg/status
     60 0
        500 http://us.archive.ubuntu.com/ubuntu/ trusty/multiverse amd64 Packages

What is causing the problem with the installation?