OneCare includes a firewall and an antivirus, but you don't configure them to allow IP addresses. The antivirus protection shouldn't be the issue, especially if it works in Firefox.
I also don't think it would be the Firewall, since it works in Firefox and Adobe Flash would be allowed to pass through the firewall.
I would suggest going to Tools/Internet Options/Advanced in IE and clicking on the option to reset everything to default. See if that resolves it as I suspect that something got messed up in the IE settings somewhere.
-steve