This crash signature is possibly related to malware:

• bug 434403 - Startup crash [@ nsDocShell::SetupNewViewer(nsIContentViewer*)] [@ nsCOMPtr_base::assign_with_AddRef(nsISupports*) | DocumentViewerImpl::Close(nsISHEntry*) ] (causes: Backdoor.Ulrbot.C Trojan, Spector Pro)

Do a malware check with some malware scanning programs on the Windows computer.
You need to scan with all programs because each program detects different malware.
Make sure that you update each program to get the latest version of their databases before doing a scan.

• http://www.malwarebytes.org/mbam.php - Malwarebytes' Anti-Malware
• http://www.superantispyware.com/ - SuperAntispyware
• http://www.microsoft.com/security/scanner/en-us/default.aspx - Microsoft Safety Scanner
• http://www.microsoft.com/windows/products/winfamily/defender/default.mspx - Windows Defender: Home Page
• http://www.safer-networking.org/en/index.html - Spybot Search & Destroy

You can also do a check for a rootkit infection with TDSSKiller.

• http://support.kaspersky.com/viruses/solutions?qid=208280684

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

SOLVED:-) Thank you. Tried Superantispyware and it found zero items. Then tried Malwarebytes and it also found zero. Then tried Microsoft security scanner and it found and removed the following: Adware:Win32/Altnet, Monitoring Tool:Win32/eBlaster, Program:Win32/AltnetP2PNetworking, Rogue:Win32/Winwebsec, SoftwarBundler:Win32/KaAzA . Rebooted computer and launched Firefox and it launched with no problems. I re-enabled all plug-ins and re-launched the browser and it launched with no problems. Thanks again!