Try to disable hardware acceleration in Firefox.

• Firefox > Preferences > Advanced > General > Browsing: "Use hardware acceleration when available"

Try to repair the disk permissions:

• http://thexlab.com/faqs/repairprocess.html

Try to remove the Firefox plist file (org.mozilla.firefox.plist).

• http://www.macfixit.com/article.php?story=20060606082246983 How .plist files become corrupt and troubleshooting the results

Go to "~/Library/Preferences" and remove the plist file for Firefox (org.mozilla.firefox.plist)

Thank you cor-el but that didn't solve the problem and the plist file for Firefox isn't showing up anywhere in my computer.

Still having this problem or were you able to resolve? I've been dealing with a flickering right-click context menu selection since about Firefox 14.

Hardware acceleration has no effect on it. Removing the plist file has no effect.

Does this still happen if you start Firefox in Safe mode?

You can use one of these to start Firefox in Safe mode:

• On Windows, hold down the Shift key while starting Firefox with a double-click on the Firefox desktop shortcut
• On Mac, hold down the Options key while starting Firefox
• Help > Restart with Add-ons Disabled

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

I had this same issue. Dual screen, right side screen drop down menus flicker out, left side screen operates normally. Dell PC Windows 7 Firefox 16 (just updated today) All Java applets up to date

I dug around and found a resolution to this problem. It's been a problem since 5.0. I have 16.0 and it still is an issue. My drop down menus go wonky, flickering, and can't be seen or legible.

The resolution I found had me fighting for the resolution because it lacked detailed steps so I'll post them here.

1. Point to "start", click. 2. Point to "Search programs and files" box and type "run" in that box, HIT ENTER. 3. With "Run" dialogue box open, type in "sysdm.cpl", CLICK "OK" button 4. In the "System Properties" dialogue box, CLICK on the "Advanced" tab. 5. Under the "Advanced" tab, in the "Performance" section, CLICK on the "Settings..." button. 6. Under this "Performance Options" dialogue box, under the "Visual Effects" tab, select the radio button next to "Adjust for best appearance". CLICK the "apply" button. 7. Lastly, under these options is a box with visual options. CLICK on the check box to remove the check next to "Show shadows under windows". CLICK "apply" button again. This worked for me.

It does occur in safe mode, but not consistently. It's more obvious in sub-menus of the context menu which safe mode doesn't always have (depending on what you're right-clicking). I'll have to see if I can pin down reliable steps to reproduce.

So I'm using Firefox for Mac, not Windows. I'm curious though if you have any similar add-ons as me.

Do you have "FFchrome" or "Save File To" installed?

@nodakgaragedoor I had the same issue (dual screen, flicker only on right screen) and this worked -- but I think the check box is "Show shadows under menus".