How do I stop Moviestorm from updating automatically?

Find your installation:
PC: Moviestorm normally installs to C:/Program Files/Moviestorm-1.4
or to C:/Program Files (x86)/Moviestorm-1.4

Mac: In Applications, right click on Moviestorm.app and select 'Show Package Contents', then browse to Contents/Resources

Within the installation folder above, look in the 'boot' folder.
PC: Open boot-win.properties in a text editor
Mac: Open boot-mac.properties in a text editor

Look for the line
update=auto
Change it to
update=yes
This will prompt you to update, when updates are available.
Or change it to
update=no
This will not check for updates at all.