Hi John,
Are you using the new Contacts Portal or the older Customer Portal? Using the new Contacts Portal I was able to create a case and assign it to a customer and then login as that customer (or one of their contacts) to the Portal and view the case. If this is not working for you can you give me details on the steps you are taking?
-Michael
Michael Melo
Product Manager
Method Integration Inc.
Website: http://www.method.me
LinkedIn: http://www.linkedin.com/in/MichaelMelo