Earlier quoted context omitted.
I think it was there throughout XP, and fixed in Vista along with fixing the "bush hid the facts" Unicode detection bug. And, well, XP is oficially EOLed, but still out there in the wild. Anyway, hand-typing ~30 full pages of text is not very likely in either case ;)
In the interests of posterity, and not because I always need to be right about everything, I just remoted into an XP Professional Service Pack 3 desktop, entered 53.2 megabytes of text, then successfully saved, reopened, edited, saved again, and reopened the document again using Notepad.
:) Now that's what I call dedication! I stand corrected.