DSM 6.x und darunter Diskstation not recognized: LED blinking

[to_sam]

I have just gotten the Diskstation 212j with a 2TB disk inside. I have done the following to install the system:

- switched on
- connected DS to router through LAN cable
- installed DSAssisant on laptop
- connected laptop (Windows8) via WLAN to the router (router works, internet connection also)
- Ran DSAssistant

Issues/Problem:
- DSAssistant does not find the DS in the network.
- The Status LED on DS is blinking constantly in orange.
- The LAN LED is off.

I can successfully connect my laptop to the DS directly and DSAssistant will find DS immediately. But once the router is between laptop and DS, DS is not found anymore. Does that have to do with port forwarding or so?

Thanks!