Hello!
When I close an opened file or exit the application without saving my changes (I press "Don't save"), the application crashes.
I use LXfree 4.0.2 on Macbook pro with OSX 10.10.3.
This issue has been fixed in version 4.0.5 and later.
This was specific to that version of LXFree and also specific to a plot that has a report tab open and the "Ask to keep changes when closing documents" option is selected in the General tab of the System Preferences.