Mirroring, replication and failover cluster are entirely different concepts. If you were experimenting with just mirroring or replication you would not be getting any clustering errors, as these technologies are independant of clustering (although they can be incorporated with clustering to an extent).

If you are reviewing SQL Server 2012 I would suggest researching AlwaysOn. It is pretty much the next version of mirroring and works with groups of databases versus individual databases which is what database mirroring does. Also from what I hear it is easier to setup as well. Additionally as of SQL Server 2012 database mirroring is now a deprecated feature in favor of AlwaysOn.