Well I know you can cause those errors by destroying a GUI Object than recreating it in the same block of code.
I.e:
PHP Code:
//#CLIENTSIDE
function onCreated() {
onCreateGUI();
}
function onCreateGUI() {
if (isObject(lolwindow)) lolwindow.destroy();
new GuiWindowCtrl(lolwindow) {
x = 30;
y = 30;
width = 100;
height = 100;
}
}