This problem developed back in january and I've been trying to fix it ever since to no avail.
The problem is, that over my shared connection, the client pc's are having some rather strange difficulties with the internet.

the setup:
host pc- running windows xp, using norton internet security.
client pc's- one using xp, one using 98SE, xp one using winxp firewall, no firewall on 98 one.
network setup modem > host pc > switch > clients, using wired network.

the problem in a nutshell:
host has full connectivity to the internet, everything works fine. The clients have a strange problem where certain things don't work. Yahoo and aim messengers work fine, msn messenger cannot connect. Some websites work (yahoo, google, this one, yahoo mail), but several dont (msn sites, hotmail, several others). FFXI, Second Life, Ragnarok online all work fine, battlefield 2 connects to account server fine, but cannot search for servers, soulseek also connects but cannot search, IRC connects to servers, but cannot join channels. Cannot run windows update.
In short, some things work fine, other things will not work at all, some things half work.
any help would be wonderful, as I rather miss having msn and irc, along with the other things I cannot use on the client pc's (of which mine is one). Preferably without removing norton (dad's liable to tell me to get stuffed) or investing in a router (system worked fine before, just went overnight).

Thankyou for any help

That sounds very similar to the setup I used to have, with the same sorts of problems too. Do you have the same problems if you disable norton on the host machine? Have you tried turning the switch off for a few minutes, then back on again?
I had to keep re-running the network setup wizard frequently.
It sounds like a firewall problem to me but it could be something to do with the switch.
I only solved my problems by investing in a router.
If you don't want to buy a router you are probably best to post each particular pc's problems one at a time.

tried disabling norton, but, as we all know, being norton, that doesn't stop it, done network setup over and over and nothing works, I tried unplugging the switch andthat's solved nothing. Tested my pc plugged directly into the modem and a friends router, and worked fine through those, I've been thinking fireall problem, but my pc is in nortons trusted zone and no idea what it could be.