DS212J not visible in Windows Explorer

[pas100]

I have set up the DS212J using a PC connected to my LAN and this all worked ok (windows 7 home)

I have a laptop connected to my network via a wireless connection and this can see the diskstationin windows explorer absolutely fine (windows 7 profesional)

Howver the PC I used to set it up Cannot see the diskstation in windows explorer - what have I done wrong?