Could someone please help?

Could be a conflict with one or more of your add-ons. Not enough information supplied to diagnose possible causes. Try the following:

Firefox Safe Mode You may need to use Diagnose Firefox issues using Troubleshoot Mode (click on "Safe Mode" and read) to localize the problem. Firefox Safe Mode is a diagnostic mode that disables Extensions and some other features of Firefox. If you are using a theme, switch to the DEFAULT theme: Tools > Add-ons > Themes before starting Safe Mode. When entering Safe Mode, do not check any items on the entry window, just click "Continue in Safe Mode". Test to see if the problem you are experiencing is corrected.

See: Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems Troubleshoot and diagnose Firefox problems

If the problem does not occur in Safe-mode then disable all of your Extensions and Plug-ins and then try to find which is causing it by enabling one at a time until the problem reappears. You MUST close and restart Firefox after EACH change via File > Restart Firefox (on Mac: Firefox > Quit). You can use "Disable all add-ons" on the Safe mode start window.

i had the same problem, nearly drove me insane!! go to 'basic troubleshooting' and follow the steps to 'reset preferences'. this worked for me although i also ran several antivirus scans.

No dropdown menu in FF will display for more than a milisecond, eliminating me from using many websites with options that must be selected via dropdown menus. Any advice for we novices??

Nevermind, see below.

It looks like this can be temporarily fixed by disabling hardware acceleration or possibly permanently fixed by updating one's graphics driver: see this thread for more details.

Does any one remember when you wold suddenly get a registry report that would tell you that it could fix all your registry errors. Suddenly I realised that it was sitting on my programs file. as this was unwanted I deleted it from my add/ remove programs via control panel. Very soon after deleting this unwanted intruding program I noted that I could no longer access my dropdown menu of any kind when I use firefox browser. I have used firefox browser for more than 6 years. This is the only thing that I recall that has caused me to ponder.. Sorry I do not recall the soft ware name however I have experienced this intruding message about my registry from old and new computers. I am thoroughly sure that that this is pay back for not subscribing to offer to clean my registrry??? Think about it ..Could this have happened to you?.. I am forced to use internet explorer as drop down menu works fine.. i just prefer firefox if the drop down menu would work again. K.

I have same issue I'm on Mac running OsX 10.5 Leopard Updated and installed newest version of Firefox 4. I have disabled all plugins and using default theme that comes installed. I disabled hardware acceleration, I tried re-starting in safe mode etc. Nothing fixed it.

Its obviously a horrible Firefox 4 bug not something on my end only. Please fix soon. I like FF, but I will stop using it forever if you cant use drop menus or forms, thats a very basic standard part of web browsing. I would rather that it worked well doing the basics before you try to add too many new features guys!

Currently my best advice to fix this issue is use another browser until FF provides an update.

Is this an interface bug?

On a clean install of Firefox 4 I had the same problem, however holding down the mouse button and dragging to the option I want works fine.

It is just when using the click and release method that the drop down disappears, this is a different behavior from older versions of Firefox where the drop down would stay shown.

I use dual monitors both using the same drivers and set to the same resolutions. Firefox works fine on one monitor but not on the other. My issue started after installing the latest Microsoft Updates.

Same with me. Problem started after a Windows update. Dual monitors, works on one (Monitor 1), problem on Monitor 2 (1 & 2 are identical Sceptre's), Windows 7 Home Premium version 6.1.7600 Build 7600, FF 4.0.1, ATI Radeon HD 5800

I have this same issue. I am using Ubuntu Linux 10 with Firefox 5 with several add-ons. I never had this problem before I upgraded to FF 5. This problem also occurs not only with drop down boxes on websites, but also on the FF menu itself (File, Edit, View, History, etc). If I restart FF, the problem goes away but ends up rearing its ugly head again until I restart FF.

I don't think this has anything to do with my add-ons at all. Its a FF 5 problem.

I have a 4 monitor setup, running Firefox 5, and drop down menus also do not work for me on any of the 4 monitors. I have another desktop computer (single monitor) with Firefox 4, and a laptop with Firefox 5, and the drop down menus work just fine on these 2 computers.

On my multiple monitor setup I use an application called Actual Windows Manager to manage my multiple monitors. When I unloaded Actual Windows Manager, the drop down menus started working just fine for me. So, in my case, Actual Windows Manager was causing the problem with drop down menus in Firefox.

Options>options>Advanced, deselect "use hardware acceleration when available"

Many Thanks this fixed my problem.

Experienced the same issue running Fedora 15 x86_64 running Firefox 6.0.2 under Gnome 3. Worked absolutely fine until the upgrade. Unfortunately, unlike others here, menus were never accessible, including at initial startup. So the suggestion to disable hardware acceleration through the menus was not an option.

Finally found a way around it. Since Gnome 3 uses hardware acceleration by default, I ended up logging out and logging back in running an alternate non-hardware acceleration desktop - in this case, KDE failsafe. This allowed me to access the menus and disable the hardware acceleration, which indeed solved the problem. I could then log back in under Gnome 3 without problems.

This unfortunately seems like a significant bug that has hit people across all platforms. I hope it's not a sign of Mozilla QA in general under the new rapid release platform. I've used Mozilla / Firefox for over 10 years as my primary browser. Something like this makes me need to take a closer look at Chrome.

Also broken in Thunderbird on Ubuntu 10.04, which updated at the same time along with xulrunner . Suggests a problem in xulrunner ?

I've been a Mozilla user for over 20 years but I don't have HOURS to spend trying to track down their programming snafu. If this isn't fixed in a few days this will push me to CHROME

Known the people that the new version becomes the top, not in the down!! The problem so easily I did not find a solution?

Just to add another tidbit. Windows 7 also just has flat out issues with multiple monitors. Esp if you don't use the Aero theme. Was getting something similar on any application menu system. I am running Aero now just to prevent that problems. I did shut down a program I was using to manage multiple monitors and that seems to have fixed it.