Forced reboot on new iMac

[elipsett]

I purchased a new iMac (27-inch late 2013, 32GB, 1600MHz, 3.2GHz Intel i5, OSX 10.9.5) recently, and use it for work which means it has all sorts of (purchased, licensed) software on it.
I normally use Firefox (latest version) with NoScript (latest version).
In spite of being a brand-new machine, the logic board died in 4 days, and was replaced. After replacement (AppleCare), the machine has developed what looks like a software problem.
I tried zapping the PRAM and reinstalling the OS. No change.
I've been slowly turning software on and off to try to localize it. The problem is that it occurs irregularly, making it hard to tell if it's gone away or is just lurking.

For the last week I had NoScript installed but disabled in Firefox, and the problem did not occur once. I turned it back on yesterday afternoon, and the problem occurred once yesterday and once already today, suggesting that NoScript is at least part of the problem.

It is not triggered by the software I am using, or what I am doing. Sometimes it occurs when the machine is idle, such as when I'm at lunch.

All of a sudden the screen displays an error message in multiple languages saying had a software problem and will restart.
It does restart, very quickly, and other than losing anything unsaved, there are no problems evident.
Various hardware tests always come back clean (Disk Utility, TechTool Pro, Drive Genius, DiskTools, Norton, MacScan, etc).
Console logs reveal absolutely nothing of any interest, and the last few entries before the restart are random (there is no program that appears frequently in the last few lines).

So.
Any suggestions on what I can try next to get a better idea of what is happening, and how to make it go away?

Thanks.

Edward Lipsett

[barbaz]

Huh, that's weird. I'm using a (older) Mac and haven't once had an issue that serious from my browser.
I think it's possible something other than the logic board is wrong with your computer...
Also, I'm not entirely sure how supported OS X 10.9 is by Firefox and other Gecko based browsers...

Does the issue ever happen when Firefox is completely shut down? (if so, not related to NoScript)
Are you using latest development build?
See what a different version of Firefox will do? E.g. try Firefox ESR?

If your Mac is crashing, look at the last few loaded kexts in the crash report, that's possibly an indicator of what's causing it to crash.

Other than that, I don't have any good ideas, sorry.