Is it crashing or just not starting? I see from your Pastebin post that there are no crash reports.

Did the Crash Report Manager come up? Did you submit the report?

Some problems occur when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

• Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
• Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet. {web link}

Unfortunately it is crashing in a way which is not letting me (reliably) submit crash reports. however I did then manage to submit one - note that the crash report did not come up, but I submitted it from about:crashes

https://crash-stats.mozilla.com/report/index/90747f94-867d-47c0-a90c-d82900171124

[I normally have to kill firefox from the task manager before it crashes - it has crashed every time, but only managed to record one crash report]

This is a corporate PC so I have no access to the (Sophos Endpoint) Firewall - Note that Firefox is able to connect to the internet & check for updates etc.

Product Firefox Release Channel release Version 57.0 Build ID 20171112125346 OS Windows 7 OS Version 6.1.7601 Service Pack 1

bp-90747f94-867d-47c0-a90c-d82900171124 Signature: IPCError-browser | ShutDownKill

Attention Sumo's there are 20 related bug reports

swi_ifslsp_64.dll = Sophos Anti-Virus

atidxx64.dll = Advanced Micro Devices

svrltwp.dll = Malware

svrltmgr.dll = Malware

You may have ad/mal-ware. Further information can be found in this article; https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware?cache=no

Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.