This looks like a problem with "Websense Endpoint" software. Websense states that it only supports the Firefox ESR version, so you can consider to switch to that version if that is possible. I don't know if they already support Firefox 45.0esr, but Firefox 38.7.1esr should work. *https://www.mozilla.org/en-US/firefox/organizations/all/ You can try to disable or uninstall this software for now until there is an update that addresses this issue, so check for such an update. You can contact Websense for support. *[https://bugzilla.mozilla.org/show_bug.cgi?id=1181091 bug 1181091] - Firefox 40 crashes on startup [@ @0x0 | ScopedXPCOMStartup::~ScopedXPCOMStartup() ] with Websense Endpoint <i>Please do not comment in bug reports<br>https://bugzilla.mozilla.org/page.cgi?id=etiquette.html</i>