I got an strange error related to this. Using IP number to get into web server
goes ok, using a DNS name is runs Ok too, but using the real name of the machine
produces:
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Bad Request

Your browser sent a request that this server could not understand.

Client sent malformed Host header

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Apache/1.3.12 Server at trsc14_40.xunta.es Port 80

I suspect DNS resolution problems in both cases.  Clients typically append a
Host: header to their requests, specifying as a virtual host the name you used
for connecting to the server.  If the server does not recognize the name as
equivalent to one of its configured hosts (or the default), it should return an
error.