>nslookup perlmonks.org
Server:  home
Address:  10.0.0.1

Non-authoritative answer:
Name:    perlmonks.org
Addresses:  209.197.123.153
          66.39.54.27
          216.92.34.251
[download]

209.197.123.153 and 66.39.54.27 work fine, but with 216.92.34.251:

>perl -MIO::Socket::INET -e"my $s = IO::Socket::INET->new(PeerAddr=>sh
+ift, PeerPort=>80); $s->print(<>); print while <$s>;" 216.92.34.251
GET / HTTP/1.1
Host: perlmonks.org
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.1
+7) Gecko/20110420 Firefox/3.6.17
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.
+8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 115
DNT: 1
Connection: keep-alive
Cache-Control: max-age=0

^Z
HTTP/1.1 200 OK
Date: Thu, 19 May 2011 06:48:47 GMT
Server: Apache/2.2.14
Content-Length: 0
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Content-Type: text/plain
[download]

The problem occurs for Host: perlmonks.org and www.perlmonks.org (the only two I tried), but "/" is the only URL I found for which the problem manifests itself.

It's not a network issue. The server is reached and gives a reply. The trace for every IP is the same save for the terminating IP.