better if
kernel.shmmax=128000000
was added to /etc/sysctl.conf file
...for the win! : }
Thanks to
simonmcnair, Silviu C., mintlxdeuser, and anyone else who may have suggested the elegant solution above. It worked great in Linux Mint 13 XFCE.
I launched a text editor (gedit) with root permissions...
gksu gedit
...via a command line and then opened...
/etc/sysctl.conf
...with it. Added...
kernel.shmmax=128000000
...to the bottom of the page and then saved and rebooted. Avast launched just fine after that.