The “You do not have sufficient permissions to access this page.” is a message thrown by WordPress whenever one of the following things happens:
1) You are attempting to access an admin page that does not exist, or is not created for your level
OR if
2) Your current user level does not have the capability manage_options
To find the issue here, please make sure that the following is all set up correctly:
Make sure that the user that you’re attempting to log in on is an admin on the specific site that you’re attempting to log in on. For instance, if you’re logging in at http://example.com/wp-login.php, your user should be an admin on your main site.
When you’re logging in, you’re being redirected to http://yourdomain.com/wp-admin/, and NOT http://yourdomain.com/wp-admin/network/. You should be getting this error as a regular admin user if you are trying to access your Network Administration panel.
If you still cannot access your WordPress Dashboard with a regular admin account after you test the above, you may have an issue with the capabilities associated with your Administrator role on your specific installation. If that’s the case, I would recommend installing a plugin such as Capability Manager, and ensure that your Admin role has the correct capabilities.
See: http://codex.wordpress.org/Roles_and_Capabilities
Please let us know if problems persist. :-)