The EXECUTE permission was denied on the object 'aspnet_CheckSchemaVersion', database 'XXX'

There should be some db roles related to the membership tables, eg aspnet_profile_fullaccess. Make sure the account you're using is a member of the appropriate role.

You should NOT assign the user you connect to the DB as dbowner privilege. The account should have only the rights it needs & nothing more. If you grant dbo & someone were to exploit a flaw in your website they would have full uncontrolled access to your entire db to what they wanted - delete tables, change data at will.

I don't think you should make the user the db_owner. I had the same problem, and it was sufficient to grand the 4 roles with BasicAccess to my user + to give him EXECUTE permission on all stored proc:

GRANT EXECUTE TO [theUserName];

I know this is not ideal. One should grant EXECUTE permissions only on the required stored proc, but if you need a quick solution until you find which SP's your user needs to be able to execute, this should work.