1. Open Firefox Options window as follows:
2. Click the menu button and select Options .
3. In the Firefox Options, click the Advanced tab, then select General.
4. In the settings list, you should find the Use hardware acceleration when available checkbox. Uncheck this checkbox.
5. Now, restart Firefox and see if the problems persist.

Hope this helped you!

Are you running Windows or Linux?

If the browser only starts with the computer in Safe Mode, then one of the other programs is blocking it.

Disable all your protection programs. After, check the firewall.

Hello,

with regards to the first solution, firefox never opens a window, just starts a process.

regarding the second solution, this is windows 7, 64 bit. I tried turning off my antivirus and that doesn't help.

firefox will load if I start windows in safe mode.

Hello, it seems whatever 49.0.1 is, it simply wont work on my computer.

I backdated to 48.0.2 and firefox works again. I'm surprised that only 2 people have this problem as noted on the count.

Hello brenaldo, I am really sorry to misdirect you with an unsuitable solution.

I agree with you, there must be a problem with your system requirements

https://www.mozilla.org/en-US/firefox/49.0/system-requirements/

i hope this link will help you understand. I suggest yo to use your Firefox with the version 48.0.2.

Thank you.!

hi, mozilla just released an update to firefox 49.0.2 that should fix a problem that sound pretty similar to what you've described. you can download this new version from https://www.mozilla.org/en-US/firefox/all/ to see if it works for you too.