so do a firefox startup in safe mode and see if the problem persists.If it doesnot persists then some add ons or plugins may be the problem. http://support.mozilla.org/en-US/kb/Safe%20Mode

Looks like a malware infection (@ fvv0mk7r.dll@0x5a82) *https://crash-stats.mozilla.com/report/index/9db42a4e-dad2-46b9-a2c3-e15c62120407 Do a malware check with some malware scanning programs on the Windows computer.<br /> You need to scan with all programs because each program detects different malware.<br /> Make sure that you update each program to get the latest version of their databases before doing a scan.<br /><br /> *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