Does it help if you also try in Windows own safe mode ?

As a clean reinstall did not help also try as a troubleshooting step creating and using a new additional Firefox profile

• Profile Manager - Create, remove or switch Firefox profiles

I suppose it is possible you could have malware so it would be worth scanning with all the tools mentioned in this article

• Troubleshoot Firefox issues caused by malware

The crash Ids may give us some clue as to what is happening. Key in about:crashes and paste in to the next reply three or four of the crash IDs beginning bp-

• see Mozilla Crash Reporter_getting-help-with-crash-reports

Do you use either Citrix Xendesk or Websense Endpoint? There might be a new issue of startup crashes with one or both of those programs and Firefox 48.

https://support.mozilla.org/questions/1133622

Thanks jscher2000,

websense was it. Creating a qipcap.dll from an existing dll in the firefox directory solves it. An empty dll will throw an error.

Is it a Firefox problem or Websense?

Thx again, A.