Hold off a little bit on downloading IE SP1...
AV = Anti Virus program. Do you remember what version of Norton you uninstalled? There are a few removal tools we can run to get what's left of the Norton off the machine, but some of them are pretty version specific.
If you have two active firewalls on the machine, turn one of them off. I'd turn the Windows firewall off as the sygate one offers a little better protection. Running two firewalls at the same time can cause issues when trying to access websites.
Then open Internet Explorer, Click on Tools and then on Internet Options. Under the "General" tab, click on "Delete Cookies" and then "Delete Files". This will effectively give you a "fresh start" when surfing to the sites you want to go to.
Try the site you are having trouble with...if you still can't access it, turn off the sygate firewall and turn the Windows one on and try again.
Let me know if this helps...