I have (had) the same problem with Xp and Firefox 3.6.3. The effects were the same as yours and also the CTRL-F to get the find line above the status line gives me a small IE find window. But the biggest problem was a phishing page when I logged to my online banking. I got a window which tells me to add 20 TAN's. I did a lot of tracing and found that there is a plugin with the name "FireFox accelerator 2.5.10.1". I searched and found the following page to uninstall the addon manually http://kb.mozillazine.org/Uninstalling_extensions. I removed the addon directory of the "FireFox accelerator" under my account directory G:\Dokumente und Einstellungen\\Anwendungsdaten\Mozilla\Firefox\Profiles\.default\extensions. This solves all known problems but not the closing of the addon window with the first click. Also a reinstallation on the same directory didn't help. Let me know if this helps you perhaps partially.

ALog

My symptoms are the same as of ALog. Today after updating to v3.6.4 the disappearing of add-ons window whenever clicking anywhere on it persists.

Has anyone an idea of reason and/or solution?

Same here: the addon window closes on the first leftclick (rightclick works!); I've just upgraded to 3.6.6 after uninstalling FF+settings and restart but problem persists. I have done a full system scan with updated BitDefender and the PC appears free of viruses.

Can't find the specific addon or directory that elgdav is referring to.

I have (and had) similar issues with Vista. Sometimes search goes to a Windows find, sometimes it's the proper Firefox search. For a while, the icons on tabs weren't displaying, but disabling and re-enabling the AVG extension seems to have fixed that. Always the Add-ons/Themes/Plugins dialog box closes on the first left click (you can click on the top header bar to move it around the screen). I've tried safe mode with the same results (which is confusing). Currently the only extensions are Java Console 6.0.20, AVG 9 and Microsoft .NET Framework Assistant 1.2.1 (which I think might be part of the issue).

In the plugins, the only odd-ball is a reference to Java Platform SE 6 U11 (as well as the up-to-date U20). The versioning on the U11 indicates 1.6.0.20. From the about:plugins, it references npdeploytk.dll which I can't find in the plugins directory at all. Could also be another culprit.

All the bizarre behaviour started with the update to 3.6.6. I've tried reinstalling Firefox with no success. I've also updated all plugins and extensions.

Me as well. Another symptom included while Firefox was already open, if I clicked on a link from an email, it tried to open a new tab but wouldn't. however, I could manually open a new tab and paste the link. Bizarre! I seemed to have corrected by doing the safemode thing and removing and resetting most items. But the disappearing add-on window still eludes me.....also since I just did this a few minutes ago, the problem might re-occur. Hopefully not but if you think the disappearing window can be solved....let me know.

Okay, so what I've found so far... since I've got it working. Somehow some trojans snuck on to my computer. AVG missed them, but MalwareBytes got them. I noticed some odd startup entries. That seemed to fix the issue with the Add-Ons dialog disappearing.

There was a "Firefox Accelerator" add-on that kept reappearing. It was gone for a while, but appeared again after scanning (I didn't install it). With the scan done, the add-ons dialog didn't disappear so I could uninstall the Firefox Accelerator successfully. I also disabled the .Net framework, and now all the search and tab functions seem to be back to normal for now.

I solved the MLCAC "Mouse Left Click Addon Close" problem on my PC. As observed by Ambrose the problem reappears after some time. I searched again with google and found some helpful hints on the german http://www.trojaner-board.de/87554-fehler-der-fire-fox-console-un... site. The problems seems to be forced by the Trojan.Agent !! A removal of the registry entry of the "Getdo" which is executed at startup and the directory ..\Adobe\Update with the critical flacor.dat (which seems to be an dll) was not possible because the trojaner was somehow resident in memory and added the deleted parts again. I booted windows in the protected mode and removed the ...\Adobe\Update directory that the flacor.dat could not be executed at startup. After rebooting normal a corresponding message appeared and the deletion was now possible. Don't forget to remove the Addon Firefox Accelarator perhaps manually like described in my previous post. Reboot again >> no message >> no reinstalled directory AND now Mouse Left Click in Addon Window is possible again.

Now I hope that this will not come again after some days.

I have discovered that MalwareBytes Free version detects and quarantines the flacor.dat ; install and run, and it will fix the problems! Note: BitDefender couldn't find it.