As I understand PCLOS if you have been updating through Synaptic since you 1st installed it you already have the 2011.6 version. You know the reloading of Synaptic, the clicking of the Mark All Upgrades, then clicking Apply. If you've been doing that you got 2011.6! there is no need for you do dl'd a new disc.
If you like the setup you have you can always use make a disc or a bootable USB for yourself.