I have just added satellite broadband onto an IBM Netvista running XP/2.

I can no longer access the music store at iTunes.  It just sits there
trying to connect.  I also run Nortin Internet Security 2004, but have
tried disabling this and it still doesn't work.  If I use a standard
dialup without proxies this works OK.

get rid of norton internet security as it is bloatware.
turn of win xp sp2 firewall

Start from here. If Itune works reinstall back the service one at the time.
Maybe your broadband satelite already has got NAT or Firewall.

Try a different firewall like zonealarm which is free.