Please keep your device and the App updated, then if the problem persists try to free resources on your device (see below), and finally in case of persistent please tell us system version installed (Menu settings> General> information> version) and if the App is in its final version (to date).
-Double tap the home button
-A bar appear at the bottom of the screen with icons for all the applications that are stored on the device.
-Press and hold one of them, a symbol ”-” will appear on each icon.
-Press the letter ”-” for each application you want to close, we advise you to do for all.
-Press again to return HOME to your home screen.
-Restart the application.
(Update iOS 7 : drag windows up to close)
For LiveCAD products contact support@liveCAD.net
For Microïds products contact firstname.lastname@example.org