Re: Failed to start firefox
uninstall Mozilla Firefox completely from your PC. At the end of it, download and run CCleaner to delete cookies, temporary Internet files and all that this show you as obsolete,
Download and run the tool v3 Advanced Care System (following the Manual) to optimize your PC in depth.
Reboot the PC and install the latest version of Mozilla Firefox browser,
Of interest: As you use Firefox, you can install IE Tab is an extension for Firefox, which lets you view Web pages with Internet Explorer engine within the Firefox browser.
Re: Failed to start firefox
If you have more than one Firefox profile, clicking on an Internet shortcut or a Web link in another application will not start Firefox 3 if you have not set the Profile Manager to automatically start Firefox with a selected profile. This is a known issue in Firefox 3 which should be fixed in Firefox 3.0.2. As a workaround, open the Profile Manager, select a profile, place a check mark in the "Don't ask at Startup" option and then start Firefox with that profile, to set it as the default.