There are two settings you could consider changing. If you change both, the second overrides the first.

• When restarting after a crash, present a screen listing earlier windows and tabs so you can choose which ones to restore, if any: set browser.sessionstore.max_resumed_crashes to 0 (zero)
• Never try to resume previous session after a crash; always go to the home page(s): set browser.sessionstore.resume_from_crash to false

Here's how:

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the search box in that tab, type or paste sessions and pause while the list is filtered

(3) Double-click the preference you want to change. In the first case, change the 1 to a 0 (a zero) and OK that. In the second case, double-clicking automatically toggles its value from true to false.

(4) You can close this tab now.

Hopefully Firefox will now behave as desired. Any luck?

Now... why is Firefox locking up often enough for you to post this question? Do you see any pattern to it (e.g., Flash games)?

Depending on how Firefox is crashing, it might be recording some data about the crashes that you can view by typing about:crashes in the address bar and pressing Enter. Check out the "Get help fixing this crash" section of the following article for tips on how to use that information: Troubleshoot Firefox crashes (closing or quitting unexpectedly).

THANKS!!! This will fix it I hope, it was exactly what I wanted! I changed setbrowser.sessionstore.resume_from_crash to false. (it was set to true)

To answer your second question... I have not figured out WHY it is doing this - it has happened twice this year only - but when it does I get into this look where some page makes it crash, then it restarts and tries to open the same page which again makes it crash... annoying enough for me to post this question to figure out how to prevent it!

Thank you, thank you, thank you!