I could be wrong here but I suspect that service pack 3 that was on my system at the time was the guilty party.
"POSSIBLY" .... I'm WINDOWS XP PRO.
I recently installed SP3.
I did then suddenly encounter stability problems with our (HJG) Boeing panels during high altitude AP controlled flight with ALT HLD selected. Although 1 or 2 people had reported this problem on our own forum I'd "NEVER .... EVER" previously experienced it with any of our B707/720's .... until SP3 went in.
I too then removed SP3 .... but .... my above problem still persisted afterward.
So .... I eventually reinstalled it again .... and still my problem persisted
I hasten to also add that around the same time as SP3 was installed I had uninstalled a number programs .... and later got to suspect that DIRECT X9C might have been "bumped" in the process.
I then reinstalled DIRECT X9C .... and suddenly my sudden and unexplained problems during high altitude AP controlled flight all "VANISHED" .... and with SP3 still reinstalled also.
I guess it's up to one's own system to make the decision