These errors will occur when the database has already been attached to a higher version of SQL Server. A database cannot be "downgraded" to a lower version of SQL Server.
For example: If a database was previously attached to a SQL Server 2008 R2 instance, it cannot be attached to a SQL Server 2005 instance.
To resolve this issue:
- Verify that the correct database server is being selected while going through the Attach Database Wizard
- Select an instance of SQL Server that would be the same version or higher, as the instance the database was attached to before.