For some strange, mystical reason, Firefox in Ubuntu simply will not connect to certain sites, like Google or www.firefox.com, but it will go to sites like this one or Customers Suck. Actually, the only sites it seems to be allowing are message boards. Even if I try a completely different browser like Lynx, it still won't go through to those addresses. Yet, when I try to visit them using the XP machine right next to me, it connects almost instantly. This is really starting to confuse me...

Lenovo 3000 J115
2GB RAM
Ubuntu 7.10

Have you check your DNS settings? Try http://opendns.com as a new DNS server. It might help.