[support] Access Denied to User #1

[Fred Jones]

On a Drupal 5.7 site when I visit /node/291 and am logged in as user #1,
I see:

Forbidden
You don't have permission to access /node/291 on this server.

but it's completely unstyled, just black text on a white page.

The page /admin/content/node of course works fine for this user, as do
MOST pages. The page /node/add however is the same "Forbidden" page.
That's in FF. In IE if I am NOT logged in at all and I visit /node/291 I
see:
HTTP Error 403 - Forbidden 
Internet Explorer 
but if I visit /home then I see the fully styled page from Drupal with
the text "You are not authorized to access this page" which is correct,
b/c the site is now not open to anonymous visitors.

When logged in as user #1 the URL /node/291/edit actually works just
fine.

This is quite bizarre, no?

Any ideas how to fix this?

Thanks.