I have the same issue. Does anyone know??
UPDATE: After some more research I found an MSDN article that might shed some light on the SharePoint's MetaWeblog API here. The article states:
"Blog API Settings With the rise of blogging, a large amount of third-party blog-writing software has been developed. In an effort to allow blog-writing software to connect seamlessly with actual blog servers, an RFC has been written for two application programming interfaces (APIs): Blogger API and MetaWeblog API. Blogger API, an older standard, dealt only with accessing the text on a blog. The newer standard, MetaWeblog API, also handles extra data such as common RSS-built metadata such as Author, Title, Comment, etc.
Windows SharePoint Services supports MetaWeblog API; when it’s enabled on the web application, users can update, edit, or create blog posts via third-party software. If you accept usernames and passwords via the MetaWeblog API, these programs can also log in to perform the updates. Otherwise, the default authentication for the site is used. If you do enable the API and allow the username and password to be accepted, note that these credentials are sent in clear text. Enabling SSL on the web application can reduce this security risk, as will be discussed later in the chapter. Leave the Blog API enabled, and turn on username and password acceptance."
Further down in the article it outlines how to setup a third-party blog posting software and states "For the remote posting URL, you’ll need to tack /_layouts/metaweblog.aspx to the end of your blog’s URL (for example, server/myblog/_layouts/metaweblog.aspx)." I'm assuming that this is the "Access Point" that Contribute is asking for.
So I had our SharePoint administrator enable MetaWeblog API and allow user/pass to be accepted and I setup the blog connection again, unfortunately to the same result. I'm thinking there are other Site Collection/Web Application settings in SharePoint that need to be set for this to work but I don't know what they would be?