Buffering using UNRAID

I have just moved to UNRAID recently. On many shows and movies, I am experiencing large amounts of buffering, rendering viewing as being unwatchable.

Can anyone please set me on the right road to addressing this problem.

PC running Windows7
Eden
Server running UNRAID with a WD Black 1.0 GB, WD Green 1.0 GN and a @GB Parity (WD Green).

Thanks.