Instead of using tween, you can simply create the fade in/out of the gui or object, by looping the objects/guis transparency up/down with a 'while' function.
e.g.
Code: ags
This makes the black gui that was initially set to 100% Transparency fade in.
e.g.
while(gBlackGui.Transparency>0)
{
gBlackGui.Transparency=gBlackGui.Transparency-4;
Wait(1);
}
This makes the black gui that was initially set to 100% Transparency fade in.