It could be caused by an application that's touching incorrect memory by attempting to null out a stride of an array, but the most common case I've seen of memory stride corruption involving nulls would be problems with the RAM itself. I don't know the mechanics behind it - perhaps a stride was touched but the data in the stride was promptly lost unexpectedly, or data is physically held on RAM chips in such manner and it's actually physically contiguous strip of memory that was lost. Dunno, all I do know is that most commonly RAM is responsible. But yes ruling out possibility of software being responsible would not be wise either.