To double check your system is clean, do the following (Not official Mozilla advice, just good practice from personal experience)

Download and Install MalwareBytes Anti-Malware, run a full Scan. http://www.malwarebytes.org/

Download and Run TDSSKiller http://support.kaspersky.com/faq/?qid=208283363

Double check for all Windows Updates.

After doing that, restart your Pc, and this time when you try to start up Firefox, hold down the shift key while it starts up. This forces Firefox into Safe mode. Let's see if that helps.

Other program found Daemon Tools file that I confirmed that is safe, but renamed anyway. Other found some files about my HTC phone and I put em all in quaranteen.

I uninstalled FF again and this time tried to install en-US version instead of Finnish. Result is still the same.

Shift clicking doesn't make any difference. FF shows in windows taskbar that it opened, but it fades away after few seconds and process still remains in Task Manager processes.

I've also had some problems with ATI Catalyst Control Center that caused blue screens for my computer and prevent me from opening some files while doing .Net programming in Visual Studio 2010. But it never caused problems with FF (atleast for now). I even tried to uninstall .Net now (don't know why tho.. :D).

I got very frustrated and was thinking of just quitting using FF but it has so good debugging tools for web-development that I really don't want to...

You have updated ATI to the latest 12.3 version?

Can you try creating a testing profile? I want to see if there is anything corrupt in your old one. https://support.mozilla.org/en-US/kb/Managing-profiles explains how

I have latest drivers.

Can't open the Profile Manager. The first time I tried it with win-button + r and then put C:\Program Files (x86)\Mozilla Firefox\firefox.exe -p it opened some window for few seconds which disappeared. After that I haven't managed to make that window appear again.

I also tried to make new profile for my Windows and log on it, but the result was same.

Do a clean (re)install and delete the Firefox program folder (C:\Program Files\Mozilla Firefox\).

Download a fresh Firefox copy and save the file to the desktop.

• Firefox 11.0.x: http://www.mozilla.org/en-US/firefox/all.html

Uninstall your current Firefox version, if possible.

• Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will also lose your personal data like bookmarks and passwords from profiles of other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other profile data are stored elsewhere in the Firefox Profile Folder and won't be affected by a reinstall, but make sure that you do not select to remove personal data if you uninstall Firefox.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox and the plugin-container process and the updater process.

See:

• https://support.mozilla.org/kb/Server+not+found
• https://support.mozilla.org/kb/Firewalls

I have done all the other things except I never touched my firewall settings.

Then I desided that one week is enought and I solved the issue with 'format c:' ;)

Don't know if messing with firewall would have helped since it only can prevent it from connecting. I didn't even get a window open that would say "Server not found" etc.. Something locked it up really badly, but now I have nice fresh intall and could get my bookmarks back from bookmark-backups that I saved.

Thanks for Tylerdowner and cor-el from answering. Really appreciate it.

Okay, I've had this on both my netbook and notebook (or laptop, if you prefer).

I'd just like to highly caution on rokoff's post here. Rather than uninstalling firefox and reinstalling it - he formatted his C: drive, and reinstalled windows + all his applications including Firefox???!!' I'm staggered at this. Be careful to all who read this (as it seems to be a common problem) DO NOT UNDER ANY CIRCUMSTANCES follow rokoff's solution to this. This will delete your entire hard drive including Windows and all your apps and data.

>>You just need to uninstall Mozilla Firefox (not your personal data tho - don't check that), and reinstall it. I've done this twice for the problem and it works fine.

It happens when the Mozilla updater service upgrades your PC to a new version automatically. First I had it on my netbook (which gets used more frequently) first and when it happened on my laptop, I thought to look around the web to see if there was another answer. ... long story short- found this thread and had to say something about that misleading "format c:" solution. Bad.

You are absolutely right homercles. I should have been more precise with the things I did before I ended up on fresh install.

My point in my last post was that I totally tried to re-install Firefox many times and did all the things other people told me to solve this problem. I even went to cycle throught windows registers manually that is also one thing that you don't want to do if you aren't absolutely sure what you are doing.

My solution was absolutely the last thing you want to do to make things work and takes alot of effort, but as I made my judgement IN MY CASE it was the only thing I could do after week of trying to fix this.