The basic problem here is that the submission of the form is using AJAX, which has a default timeout of 60 seconds. Better still, the code to modify the timeout value is located in a DLL file that we cannot easily change. So, what we have to do is figure out a way to submit the page without using JavaScript and AJAX.

I don't know if anyone needs this solution, but here is how I took care of it. Some programming knowledge is required. You will also need Firefox.

1. Increase the timeout properties in IIS for ASP Scripts and ASP.NET to about 10 minutes (600 seconds). There is ample information on the internet regarding how to do this.
2. Locate the portal signup files (admin\Portal\signup.ascx and admin\Portal\signup.ascx.vb)
3. Modify signup.ascx by placing an ASP Button next to the DNN Command Button. The ASP Button should have an OnClick property that is the same as the DNN Command Button. This is what mine looked like: <asp:Button runat="server" ID="btnHello" OnClick="cmdUpdate_Click" Text="Click me!!!" />. The reason for doing this is that ASP Buttons submit just fine with JavaScript disabled.
4. Open up Internet Explorer and browse to the Create New Portal screen. You'll see your new button here. DON'T CLICK IT JUST YET! Copy the URL from the address bar.
5. Open Firefox and go to Tools --> Options --> Content and disable JavaScript. This will force ASP.NET Buttons to post instead of using JavaScript.
6. Paste the URL in Firefox and, after logging in, fill out the information and click on the button. The form should submit normally, and because your IIS timeouts are set much higher than the AJAX timeout, you should be able to get the import done just fine.

I hope it works!