[away3d] Error #3692: All buffers need to be cleared every frame before drawing?

[John Brookes]

Just testing a model, about 8000 tri and get this error in GPU mode but not
in software mode.
Loading model and applying a light to every material, nothing else.
Any ideas?

Error: Error #3692: All buffers need to be cleared every frame before
drawing.
    at flash.display3D::Context3D/drawTriangles()
    at
away3d.materials.passes::MaterialPassBase/render()[Away3D\trunk\broomstick\Away3D\src\away3d\materials\passes\MaterialPassBase.as:192]
    at
away3d.materials.passes::DefaultScreenPass/render()[Away3D\trunk\broomstick\Away3D\src\away3d\materials\passes\DefaultScreenPass.as:404]
    at
away3d.materials::MaterialBase/renderPass()[Away3D\trunk\broomstick\Away3D\src\away3d\materials\MaterialBase.as:309]
    at
away3d.core.render::DefaultRenderer/drawRenderables()[Away3D\trunk\broomstick\Away3D\src\away3d\core\render\DefaultRenderer.as:184]
    at
away3d.core.render::DefaultRenderer/draw()[Away3D\trunk\broomstick\Away3D\src\away3d\core\render\DefaultRenderer.as:99]
    at
away3d.core.render::RendererBase/executeRender()[Away3D\trunk\broomstick\Away3D\src\away3d\core\render\RendererBase.as:305]
    at
away3d.core.render::DefaultRenderer/executeRender()[Away3D\trunk\broomstick\Away3D\src\away3d\core\render\DefaultRenderer.as:88]
    at
away3d.core.render::RendererBase/render()[Away3D\trunk\broomstick\Away3D\src\away3d\core\render\RendererBase.as:286]
    at
away3d.core.render::DefaultRenderer/render()[Away3D\trunk\broomstick\Away3D\src\away3d\core\render\DefaultRenderer.as:79]
    at
away3d.containers::View3D/render()[Away3D\trunk\broomstick\Away3D\src\away3d\containers\View3D.as:253]
    at Main/handleEnterFrame()[\JB\AW4_Truck\src\Main.as:150]