Hello AndyJTay, the Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information. Note: This will cause you to lose any Extensions, Open websites, and some Preferences.

To Reset Firefox do the following:

1. Go to Firefox > Help > Troubleshooting Information.
2. Click the "Reset Firefox" button.
3. Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
4. Firefox will open with all factory defaults applied.

Further information can be found in the Refresh Firefox - reset add-ons and settings article.

Did this fix your problems? Please report back to us!

I am afraid not. I had tried that prior to asking the question! Any other suggestions please?

I have the same problem like Andy. Mozilla Firefox Update 18.0.1 was installed on 3 computers (win7). Two have the same problem. The third one runs with version 18.0.1. I have tried several thing: Deactivating the plug-ins, the above described "RESET"-function and changing the network settings. Nothing worked. Then I've reinstalled version 18.0.0. This version works on both computers. For now, I have disabled the automatic update function.

please also see Fix problems connecting to websites after updating Firefox

Thanks a lot madperson. This solved my problems :)

After I've deleted the entry of Mozilla Firefox in my Firewall (Fritz!DSL Protect) and manually added a new entry for Mozilla Firefox everything works fine.

Well done!.

The Panda anti-virus I use was stopping it accessing the internet after the update and having reset that it is now fine.

Curious though when it worked fine on another PC and has updated frequently in the past without any problem.

Thanks all the same!

I am using firefox,since 9 years...till now i have not faced any single problem or crashed report...:)

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I was having the same problem, I fixed just right clicking > Properties > Compatibility > Run this program in compatibility mode for: Windows XP (Service Pack 3)