The key lies in what SteveEisenberg already posted:
<title>
403 Forbidden</title>
</head><body>
<h1>Forbidden</h1>
<p>
You don't have permission to access /cache/epub/2701/pg2701.mobi
on this server.</p>
For some reason, Project Gutenberg seems to dislike downloads from K3 devices. They most probably are "filtering" on the User Agent. Here's a test with wget:
Code:
$ wget http://www.gutenberg.org/ebooks/2701.kindle.noimages
--2013-02-24 22:09:15-- http://www.gutenberg.org/ebooks/2701.kindle.noimages
Resolving www.gutenberg.org... 152.19.134.47
Connecting to www.gutenberg.org|152.19.134.47|:80... connected.
HTTP request sent, awaiting response... 403 Forbidden
2013-02-24 22:09:15 ERROR 403: Forbidden.
$ wget -U "Mozilla/5.0" http://www.gutenberg.org/ebooks/2701.kindle.noimages
--2013-02-24 22:09:30-- http://www.gutenberg.org/ebooks/2701.kindle.noimages
Resolving www.gutenberg.org... 152.19.134.47
Connecting to www.gutenberg.org|152.19.134.47|:80... connected.
HTTP request sent, awaiting response... 302 Found
Location: http://www.gutenberg.org/cache/epub/2701/pg2701.mobi [following]
--2013-02-24 22:09:30-- http://www.gutenberg.org/cache/epub/2701/pg2701.mobi
Reusing existing connection to www.gutenberg.org:80.
HTTP request sent, awaiting response... 200 OK
Length: 2172590 (2.1M) [application/x-mobipocket-ebook]
Saving to: `2701.kindle.noimages'
So they disallow the download if the user agent is wget, but allow it for "Mozilla/5.0". They probably have a similar rule for the K3's User Agent - i.e., one to block the download.
You may want to contact Project Gutenberg about the issue. It's not logical for a site which is all about e-books to block downloads from e-book reader devices.