In InfoPath 2007, when you publish a form as a web form, you have the option to specify several query string parameters. One of those parameters is the "Source" parameter, which is "The location to which the user will be redirected when the form is closed. The URL must be in the same site collection or an error will be returned."
The error mentioned is "The following location is not accessible, because it is in a different site collection:" and the url you specified.
I had to come up with a solution, and a simple one jumped to mind - a redirect page!
The trick is simple. Instead of specifying a link to "http://intranet" as the source parameter (which will cause an error), specify a link to a special page in the layouts folder, and give that page the query string that links to the page you want to return to.
Confused? here is an example:
Instead of linking to the form with this link:
Link to it like this:
As you can see from the links, the first one will cause an error because we are linking to another site collection, while the second one will work, because we are linking to the current site collection.
So the only thing left for me to show you is how to create the SPSTipsFormRedirector.aspx page that will handle the redirect to the page you specified in the red section in the second link:
Open your layouts folder (C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\LAYOUTS) and create a new text file by the name SPSTipsFormRedirector.aspx. Open the file in a text editor such as notepad, and copy the following code:
string target = Page.Request.QueryString["target"];
<%@ Page Language="C#" Inherits="System.Web.UI.Page" %>
Repeate this in every front end server, and you are ready to write links to forms that, when closed, will go back to a page you specify in the link!