"the instruction at" [mem addy] "referenced memory at" "The memory could not be"

"the instruction at" [mem addy] "referenced memory at" [mem
addy] "The memory could not be".

I get that error almost thrice daily now, in almost any
application, explorer is the worst and happens most of the
time, but other apps do it as well.

I started seeing this hidious behaviour on windows 2000
after I installed SP4. Once I got windows xp I did a fresh
install, waited a while and the problem didn't show itself.
After installing sp1 though, it began happening again.

The issue is that this happens on 4 other computers I've
worked on in the last month. Two laptops (both dell, about
a year and a half a part in manufacturing times), two
desktops (one dell, the other a mishmash). My computer is a
mishmash as well, meaning no certain brand.

I find this behaviour troubling, as Service Packs are
disigned to remove bugs, not put them in.

Thanks for any help, it's appriciated.

(PS I tried using the window memory scnner from MS on my
pc, it failed 21 times on two very similer mem addys
(wmats+ mats+ and winvc tests fail), but the errors in
windows itself don't show either of these two addys. Strange.)

..__________.