NAS Drives - troubleshooting permissions

Drive: Conrad NAS (Samsung HDD)
LAN: Belkin Router
PC 1: Win XP SP3
PC 2: Win 7 Home Ed

problem:
NAS USB connected - no issues ( tried on both the XP & Win7 unit )
NAS LAN connected - discovers OK, maps OK, can see/read all files and folders but, cannot write, change or delete ( insufficient permission )

While USB connected, have set full control (drive, folders, files) for administrator, everyone, creator
Have temp switched off AV, spyware, firewall - everything I can think of

While USB connected... created a folder. Disconnect, connect drive to LAN, navigate to the folder, try to create a sub-folder - permissions error

help please,
thx