Stop re-launching apps on startup!

Not! 😝

How much was the bet for and where do I collect??

It had to do with malware taking over my Yahoo inbox and redirecting me to a Russian site which told me I had 8.264 viruses and could not be stopped/Mac was completely unresponsive other than that. Every time I rebooted after a hard shutdown, Resume obligingly loaded Firefox and the same **** site.

If Firefox was taking down your entire system, there was far more wrong than just Resume starting up Firefox again each time. Apps should not be able to take down the whole system in Mac OS X.

What an annoying bunch of nonsense..

The problem is that your computer is not behaving as it should. On a fully updated Mac, checking the box in the shut down dialog is sufficient to disable this feature. You shouldn't ever have to do what babowa recommended, but if doing that didn't fix the problem for you, you have some more significant issues. Something is not right with your system, and the question that needs to be answered is, what and where?

Try creating a new user account (in System Preferences -> Users & Groups). Log in to that account, start up a bunch of apps, then restart the machine with the "Reopen windows..." box unchecked. Does it work then?

I'm not sure I entirely understand your reply... just to clarify, are you saying that you are seeing the same behavior on two different machines? If so, that suggests that something you have done to both machines (such as some software you have on both) is causing the problem. Do you have any software installed to "clean" your computer on a regular basis? If so, remove it immediately, first because it's not needed and can be harmful (see The myth of the dirty Mac), and second because it's conceivable that such software might be causing this problem.

Alternately, what about some kind of sync software that you use to keep your user folders synced across both machines? It's possible that such software might override the fix babowa recommended, and the preference from one machine might keep overriding your settings on the other.

Firefox wasn't taking down the system as such - I fell prey to a DNS changer/redirect or some such - it had taken over/hacked into my Yahoo inbox; as soon as I clicked on the tab to access it, I was redirected to the Russian site (I believe it was MacKeeper). It took over my Mac - the only thing working was a flashing huge popup with 8, 264... and counting viruses found and another popup "we can fix this if you give us your money by clicking here". Other than that, the Mac was frozen - only way out: hit power button. Well, since FF was open when I shut down and this was before choices to disable Resume were available, it opened when I hit the button again to boot up. FF opened and immediately loaded the malware site being frozen in every other way - this was ad infinitum, until I yanked my modem cord out in order to boot without getting online automatically. I was then able to ditch history, caches, etc. However, because of this very unusual behavior, I decided it was time to do an erase and install using recovery just to be sure there'd be nothing left of whatever it was.

How long ago was this? The only likely scenario involving malware would have been RSPlug (aka DNS Changer), which stopped being a threat in late 2011. (The hackers involved got arrested and the malicious DNS servers were taken over by the FBI.) If it was more recent than that, it wasn't malware, so the clean reinstall wouldn't have been necessary. (Though it is nice sometimes to just clear out the cobwebs... I recently did a clean install, because of a few minor little irritations that I couldn't figure out an easier way to fix, and it was definitely worthwhile.)

Regarding Firefox, no matter what the site, it shouldn't have been capable of causing your whole computer to freeze. Firefox, sure, but not the whole system. If the entire system became unresponsive, there was some other issue at play, which the clean install would have taken care of.

Of course, this is getting a bit off-topic.

Just to close out this conversation: yes, it was before late 2011 - do not remember the exact date (summer?) and it was certainly the strangest thing that has ever happened to me. I don't know what caused it to freeze, but although i was able to move the cursor to the file menu, I was not able to click on/invoke Quit (FF) or Force Quit or Shutdown (Finder). Anyway, it was a long time ago - right after the introduction of Resume - and I vowed to never allow that app to be active again.

I think it's the OS.

You're welcome to believe that, but it's unlikely to be true, since most people are not seeing a similar issue, and that belief will likely prevent you from finding a solution to the problem.

The only time I've seen this happen is after powering down by holding the power button (i.e., a crash). Then it starts up and "resumes". Not saying that this is what you are doing but I have seen it "resume" even when the checkbox is unchecked.