So... the Firefox window won't come up at all, even to display an error message?

Could you try starting up in Firefox's Safe Mode? That's a standard diagnostic tool to deactivate extensions and some advanced features of Firefox. More info: Diagnose Firefox issues using Troubleshoot Mode.

Here's how: hold down the Shift key when double-clicking the Firefox icon.

A small dialog should appear. Click "Start in Safe Mode" (not Reset).

Will it start?

still doesn't work

Nothing happens at all -- no Safe Mode dialog?

Or Firefox doesn't start after you select Start in Safe Mode?

Do you get the Mozilla Crash Reporter dialog?

Before I make more suggestions, could you give more details on what is happening.

i tried once and it worked( No dialog Safe Mode appeared). I closed the browser to see if it works again, but it doesn't. No dialog appears- nothing happens!

Could you check the Windows Task Manager to see whether firefox.exe is still running? You can call it up by pressing Ctrl+Shift+Esc and then try the Applications tab first, and then the Processes tab. If you find Firefox lingering there after you shut it down, select it and End Task (on the Application Tab) or End Process (on the Processes tab). Then see whether you can start it up again normally.

Also, if you have not shut down and restarted Windows since this problem began, you might want to try that next in case some shared component in memory is malfunctioning.

"ASTROMENDA" program was the culprit all this time!!!! I removed it and my Firefox works just great!!....******BEWARE OF THIS PROGRAM******!! it will change your browser settings without you even knowing

Thank you for your help!