That's great, but DSM 6.1 on DS1513+ (arch-cedarview) has updated kernel to 3.10.102 I Think, and I am not sure all USB drivers are kompatible.
Do you use Z-stick RFLink or RFXCOM?
You can also log in to your NAS with Telnet or SSH and type: dmesg
and check if you have some USB driver errors, if not, No worries
