More investigation followed.  We've cleared our arc plugins
of all blame.  Problem seems to be that www.tv2.dk redirects
to tv2.dk, but httrack thinks those two are the same. 
However, if we use -u2, it doesn't think they're the same,
and the redirect works, but we don't get the body of the
redirection like we do with -u[01].  Strange, because the
type is well specified in all cases, so -u shouldn't make a
difference...

So it would seem that using the checker (-u2) forces the
body to be 'used up' rather than given to the plugins, and
that makes the links work.  As far as I can read the log
extract below, we get tv2.dk from the redirect, not the
body.  In the -u2 case, there is only a tv2.dk directory, no
www.tv2.dk directory, whereas with -u[01], it's the opposite.

-Lars

11:34:05        Debug:  build relative link
<http://www.tv2.dk/> with primary/prim
ary
11:34:05        Debug:  built relative link
<http://www.tv2.dk/> with primary/prim
ary -> www.tv2.dk/
11:34:05        Debug:  wizard link test at www.tv2.dk/..
11:34:05        Debug:  wizard test begins: www.tv2.dk/
11:34:05        Debug:  Compare addresses: www.tv2.dk!=primary
11:34:05        Debug:  result for wizard link test: 0
11:34:05        Debug:  Testing link type www.tv2.dk/
11:34:05        Debug:  Tested file: www.tv2.dk/
11:34:05        Debug:  wizard test begins: tv2.dk/
11:34:05        Debug:  Compare addresses: tv2.dk!=primary
11:34:05        Debug:  (Keep-Alive): successfully preserved
#0 (www.tv2.dk)
11:34:05        Warning:        (during prefetch) Moved
Permanently (301) to lin
k <http://tv2.dk/> at www.tv2.dk/
11:34:05        Debug:  File confirmed (size test): tv2.dk/ (44)