You might have disabled Firefox's use of hardware graphics acceleration before and simply not turned it off again in your new profile.

You usually need to restart Firefox in order for this to take effect, so save all work first (e.g., mail you are composing, online documents you're editing, etc.).

orange Firefox button or classic Tools menu > Options > Advanced

On the "General" mini-tab, uncheck the box for "Use hardware acceleration when available"

If you restart Firefox, is the issue resolved or at all improved?

The problem was intermittent—it didn't happen every time a specific page. However, the problem hasn't recurred with the hardware acceleration option unchecked, and I did find a couple of instances where the problem did occur after I had re-checked the box to enable hardware acceleration.

Thanks very much for taking the time to help!

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 otherwise enabled.

You can also try to uninstall Windows update KB2670838 if you have this update.

• http://support.microsoft.com/kb/2670838

Thanks, cor-el. I uninstalled the Windows update you referred to, and re-enabled hardware graphics acceleration. The problem hasn't recurred.