Weird DFrame glitch

[Sezasm]

Why is it that when I make a frame using this method:

local CFRAME = {}

derma.DefineControl( 'CFrame', '', CFRAME, 'DFrame' )

local MENU = {}

function MENU:Init()
	self:MakePopup()
	self:Position()
end

function MENU:Position()
	self:SetSize( 660, 500 )
	self:SetPos( 256, 156 )
end

vgui.Register( 'CMenu', MENU, 'CFrame' )

concommand.Add( 'cmenu', function() vgui.Create( 'CMenu' ) end )

...it looks like this with a weird graphical glitch thing in the upper left corner:
[IMG]http://i.imgur.com/aEGefex.png[/IMG]

...but when I create a frame using this method:

concommand.Add( 'cmenu', function()
	frame = vgui.Create( 'DFrame' )
	frame:SetSize( 660, 500 )
	frame:SetPos( 256, 156 )
	frame:MakePopup()
end )

...it creates a perfectly normal frame?:
[IMG]http://i.imgur.com/H2glQVX.png[/IMG]

[BoowmanTech]

in vgui.Register instead of CFrame use DFrame.

[Sezasm]

Yeup, that fixed it, thanks