I have configured WSS with OpenID to enable FBA authentication. I have added a custom login page. Im able to authenticate using the OpenID account, however when i return back to the default.aspx page i get the 'Access Denied' page.
The Question is how can i tell WSS to allow OpenID authentication into the web application?
I have used the DotNetOpenId library.
I haven't integrated with WSS myself, but assuming you have it in FormsAuthentication mode, then the only other thing I think that could be blocking you would be that while you are logging the user in (with SetAuthCookie or RedirectFromLoginPage) you need to pass in the roles the user belongs to. If WSS is rigged to only invite users in the "WebUser" role, for example, be user to pass that into the login methods.
You can find out what roles are required and what your Authentication mode is from inspecting your WSS site's web.config file.
If you are using FBA you can add the openid account as an fba account. You can easily do this by using a custom login page. Here is a sample http://blog.xsolon.net/Posts/sharepointopenid.aspx