So Insufficient Stack Space is only or more of a software-related error than a hardware one?

>>But why does it happen on just a few select PCs?
>
>Clearly, something is different with those PCs. If it's not software, maybe components are slightly different (even though they're all supposed to be the same). Or, hardware may be failing intermittently - bad memory chips etc. Although I'd discount hardware problems if it's happening to 5 rather than just 1 or maybe 2. Also, hardware problems don't usually product "insufficient stack space" errors.