Oops... I modified the signup script yesterday to make the fact that we don't give away .com's for nothing even more obvious, but looks like the Javascript I added doesn't work with IE.
What is your domain name? Have you already registered it? If so, set your nameservers to ns1.heliohost.org and ns2.heliohost.org. If not, then request that I delete your existing account so you can make a new one.