Networking – Painfully slow transfer speeds on Synology DiskStation DS412+ NAS

I've just bought a Synology DiskStation DS412+ and put 2 x 3TB Western Digital Red drives in it, set up in RAID 0. It's currently plugged in to my gigabit Netgear switch.

I created a user with full permissions on the NAS, created a share, mapped a drive on my Windows 7 PC (also gigabit ethernet) and tried copying some files, but I'm getting painfully slow transfer speeds (< 40KB/s – yes, kilobytes, it's not a typo!

Does anyone have any ideas why it'd be so slow? There's loads of reports online of people getting > 80MB/s from this NAS.

I've copied files from this PC to my MacBook Pro in the past and got decent enough speeds so it shouldn't be an issue with the NIC on this PC, or (hopefully) the Netgear switch it's going through.

Thanks

Edit – Resources are pretty low..