Try to disable hardware acceleration.

• Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available"

If disabling hardware acceleration works then check if there is an update available for your graphics display driver.

• https://support.mozilla.org/kb/how-do-i-upgrade-my-graphics-drivers

I had that problem to, but I realised that the problem is with the anisotropic filter, if you use nvidia go to its control panel > 3D configuration > program configuration Find in that list, Mozilla Firefox and set anisotropic filter "manage by aplication" And of course there is no need to disable hardware acceleration sorry for my English take in mind that I don't use it in English so I don't know exactly how they are named. I hope that work for you