extreme cpu usage with nndir (on specific files)

[Harry Putnam <reader@newsguy.com>]

I've run into a problem this morning that has me somewhat stymied.

Using gnus to create an nndir group of an archive I want to copy to a
second nnml server.
The directorys look like ~/00 ~/99 ~/98 and contain messages from
those years.

With file names like so:
awk00:

  00853
  00854
  00855
  00856
[...]

The biggest directory contains some 3000+ messages, the other
two have under 2000 each. 

Making an nndir group of anyone of them causes gnus to go into a spasm
of cpu usage that seems clear out of line with the job at hand.

Watching top display I see cpu pegged near 99 % and memory around 42%.
This lasts for a very long time, like 5 minutes.  Just to get to the
point where gnus asks how many messages I want to see.

Answering with <RET> and the cpu usage is pegged again for an even
longer time.  Eventually the group appears.  After sorting date and
marking with `M P a' (both seem to take unduly long as well).  Then
copy to the desired group.  The copying is also very very slow.
 
These files have the following format:

These two line are the first two headers in every post:
#! rnews 1596
Xref: news.demon.co.uk comp.lang.awk:8026
REST OF HEADERS
BLANK LINE
body
body

I wondered if the "#!" may be causing all the commotion?

I've also tried it with a vanilla emacs and gnus on  a dummy account, but 
still see the hefty cpu usage etc.  Seems it must be something about these 
particular files.