firefox plugins youtube downloaderFirefox isn't working properly, help please?

For the past few months when I use Firefox it doesn't work properly.
Here is a list of things I can't do using Firefox:
*I can't bookmark anything.
*The "forward" button doesn't work.
*Sometimes the "back" button doesn't work, but sometimes it does.
*The drop down menu won't show up when you type in a website.
*On Google, the auto-complete drop down menu won't show up.
*Sometimes Firefox will freeze.

If it helps here is a list of the add ons I have installed:
*AdBlockPlus -- Enabled
*BetterPrivacy -- Enabled
*Easy Youtube Video Downloader -- Enabled
*Echofon -- Disabled
*Flagfox -- Enabled
*GooglePreview -- Enabled
*Greasemonkey -- Enabled
*ImTranslator -- Enabled
*McAfee SiteAdvisor -- Enabled
*Morning Coffee -- Enabled
firefox plugins youtube downloader*Read it Later -- Enabled
*TabRenamizer -- Enabled
*WOT -- Enabled

Here are the plugins I have:
*Adobe Acrobat -- Disabled
*Google Update -- Enabled
*iTunes Application Detector -- Enabled
*Java(TM) 2 Platform Standard Edition 6.0 Update 10 -- Disabled
*MetaStream 3 Plugin -- Disabled
*Microsoft DRM -- Disabled
*Mozilla Default Plug-in -- Enabled
*QuickTime Plug-in 7.6 -- Disabled
*Shockwave Flash -- Enabled
*Windows Live Photo Gallary -- Enabled
*Windows Media Player Plug-in Dynamic Link Library -- Disabled

Here are the themes I have:
*Default
*MushroomKingdom
*Phoenity Modern (This is the theme I am currently using)

I had noted whether i I had an add on/plugin enabled or disabled if that makes any difference.

I, also, have trfirefox plugins youtube downloaderied uninstalling and reinstalling firefox.

So if anyone has had any similar problems or knows and ideas of what I should to do fix Firefox, please let me know!

Your help is greatly appriciated.
Download and install the FEBE add-on. Back up your add-ons. Download - don't install - Firefox. Uninstall Firefox - completely. Reboot. Install Firefox - no add-ons or plugins. See if it works. If not you have something else wrong. (So install FEBE and restore all your add-ons.)

If it works, add your add-ons, one at a time, and use Firefox for a few days. When it stops working you'll know which add-on caused it. (Some of them can interact with others.)