SSO with ASP.NET application - exceptions

I am trying to get SSO to work from Enterprise Portal to our own ASP.NET application. Originally I tried to do this with ticket based SSO but I think this requires some coding on the ASP.NET side which I am trying to avoid for now.

Since then I have tried to achieve SSO using this document:

/people/sap.user72/blog/2004/11/30/user-mapping-based-single-sign-on

Our app uses form based authentication and I can call our app via this method (tested in browser and it works): http://servername:port/resource.ext?login=<mappeduser>&passwd=<mappedpassword>

However after I configure the URL iView for GET method and the required system (with alias) per the instructions it does not work when I try to Preview the iView. I get an exception:

"An exception occurred while processing a request for :

iView : pcd:portal_content/Main

Component Name : com.sap.portal.httpconnectivity.urliviews.runtime

Can't read the prameter 'siteString' from the PCD..

Exception id: 09:49_14/07/05_0029_8788250

See the details for the exception ID in the log file"

The log file does have a lot more details but nothing that I can make sense of - I can post the details if it helps.

I've seen others have this problem but it doesn't seem like everyone has resolved this. By the way I have already ensured that permissions for the iView and the system allow "Everyone" to have Full Control so I don't think its a security issue.

Any ideas how to solve this? Or where to look next?