Have you checked the proxy settings?

• see also firefox cannot load websites but other programs can

What happens if you use Firefox to navigate a local disk drive, does that work ok ?

I hope you are using separate profile for each firefox version.

Sorry, but I read that page before I posted my question. I followed the instructions on it, but no luck :(.

I'm able to load html files that I have saved on my hard drive.

What do you mean by separate profiles? Currently, I only have Nightly installed on my computer. I tried switching versions, thinking that it was only a bug in the Nightly build, but no luck.

I found that Firefox will load pages only on the first start up; that is, when I check "Launch Firefox" in the install window, it works just fine. But anything after that initial start up fails.

Nightly is intended mainly for developers or advanced users and is likely to be subject to revisions. It is however a good idea to test whether problems occur on nightly versions, because some problems may have been already solved on nightly but not yet on other releases.

The use of profiles is not totally straightforward, and if you have only one version of Firefox installed at any one time, normally you will not need to understand how to use multiple profiles. If for any reason you do use multiple versions of firefox then have a look at

• http://kb.mozillazine.org/Using_multiple_profiles_-_Firefox

There is one other use for multiple profiles which could be highly relevant to your problems. Creating a clean profile is a troubleshooting method, and by creating an additional profile you are able to keep a current profile (which may have your passwords and bookmarks etc) whilst also having available a minimal clean profile for testing purposes.

• see http://kb.mozillazine.org/Profile_Manager
  (profile manager is being phased out soon, and a method of easily doing a clean reinstall is being introduced )

Another important troubleshooting step is using a clean reinstall that is explained here:

• http://kb.mozillazine.org/Standard_diagnostic_%28Firefox%29#Clean_reinstall
• take care when doing that do NOT delete profile files, or use the option to delete personal settings (the file to delete are in the Windows Programs path)

I did a clean install and removed all the personal data. I don't have personal settings that couldn't be easily set back.

I launched Nightly again, but the problem persists. Does Nightly delete all the registry files when it uninstalls? Do you think there could be a problem with one of the registry files?

Did you check the proxy and connection settings that aurora is using ?

• Nightly Button -> Options -> |Advanced| -> |Network| connections
• see Advanced panel - Accessibility, browsing, network, updates, and other advanced settings in Firefox connection-settings-dialog

I Note you mentioned you did a clean install but deleted the profile, the clean install should delete the program files as well did you try that ?

I am not sure Firefox uses the Windows registry for anything much of importance, other than file associations. It seems odd it works initially and then fails. Any adjustments to settings from a profile or from the program folder would normally be set on the first run I believe, although someone may correct me.

My suspicion is that some other software, presumably malware is making changes after the installation. See is my firefox problem a result of malware

Or some security software/firewall is blocking it, but again I do not see why that should be a delayed affect - I can understand security software recognising one version but not another, but do not see why it would run once but not a second time.

• see also cannot connect after upgrading Firefox

Other than the above I am afraid I have run out of ideas.

I've done a full scan with Avast and Malwarebytes. I already said I turned off all of my firewalls. I did delete the program files. I have the proxy settings set to "No Proxy".

Thanks for the help, but I give up. I'm just going to use Opera.