Use Older Versions Of SQL Server Databases With 2012?
The version (539) indicated in the error message says that this database is a Sql Server 2000 database and thus is not supported in Sql Server 2012 See here

Probably in your SqlServer 2008R2 this particular database has a compatibilty level set to Sql Server 2000. You could try to change this level going to the properties of the database, Options page  and changing the compatibility level to 2008, then retry to attach the database to Sql Server 2012