Note: not an issue in 3.6.2.
To reproduce method 1:
Start a level, start GUI editor (F10), close it, reopen GUI editor (F10), close it again and crash/lock.
The error which loops into eternity.
To reproduce method 2:
At MainMenu open GUI Editor, close it, open it again and close aghain and crash/lock.
To reproduce method 3:
Open GUI Editor once, then exit and quit Torque. Lots of errors but T3D will quit before it locks.
The error which loops to crash:
tools/guiEditor/scripts/guiEditorCanvas.ed.cs (223): Unknown command delete.
Object (4479) MenuBuilder
The script: tools/guiEditor/scripts/guiEditorCanvas.ed.cs
/// Called before onSleep when the canvas content is changed
function GuiEditCanvas::onDestroyMenu(%this)
{
if( !isObject( %this.menuBar ) )
return;
// Destroy menus
while( %this.menuBar.getCount() != 0 )
%this.menuBar.getObject( 0 ).delete();//yorks - here be dragons!
%this.menuBar.removeFromCanvas();
%this.menuBar.delete();
}
Suggest:

Bonus Suggestion:
A dedicated bug forum for checking stuff might be useful.