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

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.org/kb/Safe+Mode

Thank you very much that solved the problem.

I am having the same exact problem, all of my drop down menus seem to flash and then disappear. I tried the stated solution but it did not work. I tried disabling hardware acceleration, safe mode and updating my graphics card driver. Please help, I love Firefox and I would hate to have to use a different browser. I am using windows 7 and a NVIDA 500 series graphics card if offers any info.

The solution worked for me. Read the directions again and try it one more time.

I tried everything as mentioned my graphics card is up to date, I disabled everything from add-ons to hardware acceleration and WebGL, I reinstaled and repeated the steps again to make sure. I am seriously stumped...