Set Cube URLs from an action creates error No device compatible image available…

With the flash viewer this code works fine

set(image.level[0].tiledimagewidth, 956);
set(image.level[0].tiledimageheight, 956);
set(image.level[0].front.url, panos/View_1.tiles/f/l1/%v/l1_f_%v_%h.jpg);
set(image.level[0].right.url, panos/View_1.tiles/r/l1/%v/l1_r_%v_%h.jpg);
….
….

but the HTML5 viewer returns the error - No device compatible image available…

Is there a problem in HTML 5 with setting image URLs from an action?

I've had to find a workaround for this problem using the text add command

e.g.

txtadd(scene[%1].content, get(scene[%1].content),
'<image type="CUBE" multires="true" tilesize="512">
<level tiledimagewidth="1910" tiledimageheight="1910">
<left url="panos/View_%2.tiles/%s/l2/%v/l2_l_0%v0%h.jpg" />
<front url="panos/View_%2.tiles/%s/l2/%v/l2_f_0%v0%h.jpg" />'
);

it's a shame that the code that's useable for Flash is now not working with HTML5.