This is an oft-revisited topic. Something hotly debated, primarily 
because the simple definition of pareve as dairy-free is nowhere near 
that simple (nor are many Jewish laws very simple, IMHO).

It is the case that, by following equipment cleansing rules, dairy 
lines can be "flushed" and rendered pareve. Many believe (and have 
the experience to back up the belief) that such a cleansed line can 
retain enough contaminant particles to provoke symptoms.

You can find a good and relevant discussion here: http://nomilk.com/parve.txt

The laws of kashrut - whether something is kosher, whether it's 
deemed Dairy or Meat or Pareve (neither) - are religious laws, but 
not entirely absolute in a scientific definition. (one perspective 
here: http://www.ou.org/kosher/primer.html, with a few insights here: 
http://www.kashrut.com/trade/trade_links/wheycream/).

It's really quite complicated. A lot depends on which supervising 
agency has bestowed its "hescher", or seal, indicating whether the 
food is kosher and pareve. (heschers here: 
http://www.iprofess.com/foodlabels.htm  and even more here: 
http://www.kosherquest.org/index.asp?theaction=symbols ). Each 
follows slightly different rules regarding both the designation of 
something as pareve and the labeling. You can sometimes find at 
"D.E." label, that indicates that a food has been prepared on dairy 
equipment. But not all supervising agencies do so. And some, I 
believe, allow a food line to be declared pareve after the line's 
been flushed.

This little blurb is somewhat relevant:
A few of the supervising agencies permit the use of a "D.E." symbol 
next to their kosher symbol, for "dairy equipment." This means that 
the product has all pareve ingredients but was made on a dairy 
equipment line. The rules for using such products in a kosher home 
with a meat meal are complicated and some agencies have therefore 
decided not to allow their food companies to provide this 
information. However, this information could be very useful for 
non-kosher observant consumers.
That would be us.

Mark

At 01:48 PM 2/24/2008, you wrote:
>If it's marked Pareve, it has to be made on a dairy free line, otherwise it
>would be marked D. If you have a problem with it, it may be something else in
>it  not related to dairy.