According to your crash reports..... You have too many extensions installed whose author not verified and the last most important thing is that it contain malware namely... lpxpcom.dll and nvwgf2um.dll so kindly do the following steps:::

Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• Anti-Rootkit Utility - TDSSKiller
• AdwCleaner (for more info, see this alternate AdwCleaner download page)
• Hitman Pro
• ESET Online Scanner

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

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Separate Issue; Your System Details shows;

Installed Plug-ins

Shockwave Flash 15.0 r0 Shockwave Flash 14.0 r0

Having more than one version of a program may cause issues.

Grab the uninstaller from here: Uninstall Flash Player | Windows Uninstall Flash Player | Mac Then reinstall the latest version.

Flash Player v15.0.0. 239 http://get.adobe.com/flashplayer/

The crash reports flagged these programs;

lpxpcom.dll = LastPass

nvwgf2um.dll = NVIDIA Compatible D3D10 Driver

JavaScript

Some added toolbar and anti-virus add-ons are known to cause Firefox issues. Disable All of them.

Perform a System File Check to fix corrupted system files http://www.sevenforums.com/tutorials/1538-sfc-scannow-command-system-file-checker.html

See if there are updates for your graphics drive drivers https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

Hello,

Also, you can delete in your profile folder the User.js file you have.

The user.js file does not exist by default. If you create the file, forget it, if you have not create the file then delete the User.js file, to see if the problem goes away (some programs create and write in the file also).

maybe not related but see for your screenwise extension :

http://www.engadget.com/2012/02/08/google-screenwise-panel-pays-to-track-browsing/

http://www.tomsguide.com/us/Google-Chrome-Screenwise-Data-Collection-Plugin,news-14172.html

https://tools.google.com/dlpage/screenwisepanel/ :

(If installed, this extension will check if a person is signed in to a Google account, and shares that account information with Google servers to verify whether the user is a registered Screenwise panelist.)..... privacy ?

thank you