Why might the enabled Direct2D not work in Firefox?

Question

Mozilla Firefox

One of the many machines our firm has tested renders graphics in Firefox as if it has Direct2D disabled (other machines have exactly the same behavior when gfx.direct2d.disabled is set to true), even though it is not disabled. More specifically, this is shown in the display of jumps instead of smooth animation (both by means of SMIL and Javascript) in SVG when using a filter with feSpecularLighting and especially feGaussianBlur. This also breaks the animation on other SVGs on the same page, even if they do not use this filter.
Versions of Firefox on this machine were tried the same as on the rest - 29th and 33rd. The 29th version was tested "clean", immediately after installation from the same distribution kit (as on other machines), without add-ons. The gfx.direct2d.disabled option is false by default. DirectX 11 is installed, checking it through dxdiag does not reveal any problems. NVidia video card, driver just updated. RAM 16GB, and indeed the machine is not the weakest.
What could be causing this behavior? Where and how to dig?

Answer 1

Look at the about:support page in the "Graphics" section for hints.