[ubuntu-uk] IRC - does not connect

[Mac]

I thought I'd have a go with IRC.  I've set up an account in 
Xchat-gnome, but it does not make the connection.  All I get is

  Looking up irc.ubuntu.com..
  Connecting to chat.freenode.net (209.177.146.34) port 6667..

and then it just hangs.  I get the same thing with other channels;  and 
the same thing happens if I try using Pidgin.

I can't see anything in my router blocking IRC.  I know nothing about 
configuring IPtables, so these are in the default state AFAIK.  I've 
spent a good while searching the web, to no avail.

I'd be grateful for simple, specific advice about how to investigate / 
fix this.

TIA

Mac