Try to set the gfx.content.azure.enabled pref to false or if this
didn't help disable Direct2D by setting the gfx.direct2d.disabled pref
to true on the about:config page and leave hardware acceleration
The actual problem (atleast for me and a few others) is due to a
windows update kb2670838. This update applies performance patches to
Direct2D, 3D, and Write related components. The reason disabling usage
of Direct2D or hardware acceleration fixes it is because its simply
not using those Direct___ functions anymore.
In the Update history, 2670838 is listed as: Platform update for
Microsoft Windows (KB2670838) In the Installed updates, 2670838 is
listed as: Update for Microsoft Windows (KB2670838)
Again, uninstalling this update solved the problem for me and a few
others, hopefully it will solve your problems correctly as well.