If you are using PostrgreSQL you will need to upgrade hibernate.
If you know this, could you please tell us which version of Hibernate corrects the problem?
I have browsed the Hibernate JIRA and did not find any issue regarding PostgreSQL and views.
I have tried the upgrade as suggested and it works for me. I can now map a Postgres database view to a table - and works like a charm.
I found this JIRA for hibernate 3.2.6 which seems to relate to this fix: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1329
I'm using JBoss 4.2.2GA, Seam 2.0.1GA.
I found that for the hibernate upgrade to work I had to put all hibernate libraries in the server/default/lib directory and remove the hibernate libraries from my Seam EAR project.