I am not sure we fully support Nightly on this forum, and you are probably aware Nightly is expected to crash more often than the standard Release it is experimental.

• Do you have other versions of Firefox installed also ?
  You should not rely on Nightly. Does your other version work OK ?

1. Please try starting in safe mode. See Diagnose Firefox issues using Troubleshoot Mode
   Holding the shift key whilst clicking the icon should do that.
2. Try with a clean profile, and in safe mode
   Profile Manager - Create, remove or switch Firefox profiles_creating-a-profile
3. Try a clean reinstall (Because Nightly updates frequently a bug may have been fixed already) Again try this in a clean profile and safemode.
   See Troubleshoot and diagnose Firefox problems_7-reinstall-firefox
   Note to delete the programs folder NOT the profile folder
4. If you still crash please provide a couple of the latest Crash IDs they begin bp- and are obtained by navigating to about:crashes
   see Troubleshoot Firefox crashes (closing or quitting unexpectedly)_get-help-fixing-this-crash
   But please post back in this thread not the special link in the article.

You may also get information and help with Nightly on mozillazine

• http://forums.mozillazine.org/viewforum.php?f=23

edit: fixed mozillaZine links as they were to Thunderbird Builds and bugs.

Please post back with how you get on.

Hello John, I've found a solution for the problem. My COMODO Firewall was causing the problem, after uninstalling the Firewall everything is working fine. Thanks for your assistance in this matter.

Glad to here the problem is sorted out and thanks for posting back.

I will unmark my post and mark your last post as the thread solution.

Some background information:
I asked whether you are are also using another version of Firefox, because the Nightly is intended mainly for testing. I did wonder if you would need help in installing multiple Firefox versions.

• http://kb.mozillazine.org/Testing_pre-release_versions#Installing_multiple_versions
• http://kb.mozillazine.org/Using_multiple_profiles_-_Firefox

Security related problems after upgrades are possibly more likely to be blocks rather than crashes, and hopefully are resolved by reconfiguring rather than disabling or removing security software.

• Fix problems connecting to websites after updating Firefox
• Configure firewalls so that Firefox can access the Internet

I am using two version of Firefox, the standard release and the Nightly builds with two separate profiles. I also tried to launch it in Safe mode, with a clean reinstall, and with a new profile.

I found the solution for the error in the Mozilla Bugtracker

I've just made a clean reinstall of the COMODO Firewall and everything seems to work fine now.

OOH 64 bit Nightly on Windows
I had overlooked that
(Info aside User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:27.0) Gecko/20100101 Firefox/27.0)

I am not even sure 64 bit on Windows gets all updates or even produces proper crash report ID s. I use 32 bit Nightly on Windows and 64 bit on Linux. Well done with finding
Bug 652747 - 64-bit (Win64) Nightly [build 25-04-2011] crashes on launch in DLL Blacklist code with certain antivirus software installed

That Bug now appears to have been fixed I note you were able to reinstall COMODO..

Background information on 64bit Firefox & Windows

• Why firefox 64 bit for windows is not available? /questions/944092
  • http://www.computerworld.com/s/article/9234997/Mozilla_compromises_on_x64_Firefox_after_user_backlash

Really awesome stuff...

The Win64 nightles do still indeed get updates like the Win32 nightlies. As long as you do not use any builds from a Tinderbox link as they have a channel of default which gets no updates.

Also the Nightly and Aurora channel builds gets checkins pretty much everyday so therefore they get a update each of those days.

Also the Win64 nightlies are in tier3 support meaning that if a issue arises in build or build machines it is not a priority to fix them right away. https://developer.mozilla.org/en-US/docs/Supported_build_configurations

Thanks for clarifying that James. I will bookmark your MDN link for future reference.