What were you doing during the crash? Are there other crashes?

Product Firefox Release Channel esr Version 38.8.0esr Build ID 20160420141331 OS Windows 7 OS Version 6.1.7601 Service Pack 1

Signature: nsStreamCopierIB::DoCopy

sysfer.dll = Symantec CMC Firewall

IPSEng32.dll = Symantec Intrusion Detection

Download the current full installers for your Norton programs and save them.

Download and run the Norton Removal Tool to uninstall your Norton product

After rebooting the computer, run a registry scanner. Then run the installers.

https://support.norton.com

http://community.norton.com/

hi, thanks for providing a crash report id. this may be an issue caused by your norton security software that is hooking into firefox and causing it to crash (maybe through a program/signature update done by them). can you please try to disable norton temporarily and see if you can get firefox to launch again & please also get in contact with their support...