[flexcoders] ArgumentError: Error #2004: One of the parameters is invalid@Graphics/drawRect

[method_air]

This error started appearing, (the stack trace only has information relating to 
flex sdk classes), anyone know how to fix it:

ArgumentError: Error #2004: One of the parameters is invalid.
        at flash.display::Graphics/drawRect()
        at 
spark.primitives::Rect/draw()[E:\dev\4.5.1\frameworks\projects\spark\src\spark\primitives\Rect.as:463]
        at 
spark.primitives.supportClasses::StrokedElement/updateDisplayList()[E:\dev\4.5.1\frameworks\projects\spark\src\spark\primitives\supportClasses\StrokedElement.as:143]
        at 
spark.primitives.supportClasses::GraphicElement/http://www.adobe.com/2006/flex/mx/internal::doUpdateDisplayList()[E:\dev\4.5.1\frameworks\projects\spark\src\spark\primitives\supportClasses\GraphicElement.as:3958]
        at 
spark.primitives.supportClasses::GraphicElement/validateDisplayList()[E:\dev\4.5.1\frameworks\projects\spark\src\spark\primitives\supportClasses\GraphicElement.as:3942]
        at 
spark.components::Group/validateDisplayList()[E:\dev\4.5.1\frameworks\projects\spark\src\spark\components\Group.as:1087]
        at 
mx.managers::LayoutManager/validateDisplayList()[E:\dev\4.5.1\frameworks\projects\framework\src\mx\managers\LayoutManager.as:736]
        at 
mx.managers::LayoutManager/doPhasedInstantiation()[E:\dev\4.5.1\frameworks\projects\framework\src\mx\managers\LayoutManager.as:819]
        at 
mx.managers::LayoutManager/doPhasedInstantiationCallback()[E:\dev\4.5.1\frameworks\projects\framework\src\mx\managers\LayoutManager.as:1180]
        at flash.utils::Timer/_timerDispatch()
        at flash.utils::Timer/tick()