what is wrong with this gui script?

function goLeft()
	script.Disabled = false
	wait(.5)
	script.Parent.Parent.Right.Visible = false
	for i = 1,56  do
		script.Parent.Parent.CustomClass1.Position = script.Parent.Parent.CustomClass1.Position - Udim2.new(-.25, 0, 0, 0)
	Script.Parent.Parent.CustomClass1.Visible = false
	script.Parent.Parent.CustomClass2.Visible = true
	script.Parent.Parent.CustomClass2.Position = Udim.new(15, 0, 1.5, 0)
	for i = 1, 48 do
		script.Parent.Parent.CustomClass2.Position = script.Parent.Parent.CustomClass1.Position - Udim2.new( -.25, 0, 0, 0)
	end
	script.Parent.Visible = false
		end 
	script.Disabled = true
end
script.Parent.MouseButton1Down:connect(goLeft)

it says "Players.Player1.PlayerGui.ScreenGui.CustomClass.Left.Script:6: attempt to index global 'Udim2' (a nil value)" also for some reason it wont let me click it, i made the transparency 1 if that matters also, its a text button, all my other text buttons are clickable but not this one any idea why?

Udim2.new should be UDim2.new (note the capital D).

First, as MRFlimsy wrote, Udim2.new should be UDim2.new ; and in line 9 you wrote Udim.new, where it must be UDim2.new

Hope this helps,

mranderson11