Make sure you are using the latest version of TwistedBrush version 17 or later.

For older versions of TwistedBrush set DEP to only manage Windows services and internal programs.

Alternately you can keep the setting for DEP on for all programs and add tbrush.exe to the list of exceptions.
Click the [Add] button and browse to tbrush.exe, usually in "C:\Program Files\Pixarra\TwistedBrush" and say Open, double check that it is now in the list and checked, and then say OK