I just ran into this when trying to validate a SharePoint (2010) site from within CRM2011. Here’ what I did to solve it:
- Add the site you’re trying to validate against (https://sp.contoso.com) to your trusted sites in IE.
- Drop the trusted sites level to Low
- Click validate (which then the site should validate)
- Make sure to set your trusted sites back up to Medium when done.
Hope this helps!