Sometimes the stub installer -- which connects back to Mozilla for additional files -- is blocked by security software.

Could you try the full installer from this page and see whether that works better (scroll down to your preferred language):

https://www.mozilla.org/firefox/all/

I tried the full installer and it gave me the same message with a different error code (0xc00005).

When I look up that error on Microsoft's forums, I find suggestions ranging from an incompatible update/hotfix to malware...

• the application is unable to start correctly 0xc0000005 after windows - Microsoft Community
• The application was unable to start correctly (0xc0000005). - Microsoft Community
• The application was unable to start correctly (0xc0000005). - Microsoft Community

(There are many more along these lines)

I have exactly the same problem that I cannot open Firefox now. Even if I try run firefox.exe -p I get same message but with (0xc0000022). I have tried all kinds of remedy. Internet Explorer also not opening, but strangely Chrome is OK.

Hi iantwebb, there seem to be a very diverse range of problems that can cause that error, as shown in this Google search:

https://www.google.com/search?q=application+unable+start+correctly+%280xc0000022%29

Since IE won't start either, I suggest posting on Microsoft's support forum since they obviously are much more familiar with the clogs in the plumbing that cause this than we are here.

I ended up solving this problem by doing an in-place reinstall of Windows 7. It took a little bit of time but fixed this and a couple of other issues I was having.

I have no source to reinstall pre-installed windows 7 at present. What would I need?

This blog entry helped me, http://www.sevenforums.com/tutorials/3413-repair-install.html

Or do a web search on repair install or in-place install and review the results. I did this with Windows 7 although I believe it can also work for Vista. I'm not sure about Windows 8 or 8.1.