After some googlin and testing I resolved the problem of not detecting any shareport (usb) devices on the dir-855. I'm running Win7 x64, dir-855 (hw A2, fw 1.21EU) and kept getting the following error message 'no device servers were found on the network' when using the PC SharePort Utility 3.0.
The problem was resolved by using the 1.17 version of SharePortUtility. Shareport utility version 1.17 can for example be found on the Swiss dlink site.
ftp://ftp.dlink.ch/dir/dir-855/driver_software/
I didn't need to flash the firmware or open any particular ports on the dir-855, which were suggested on some sites. My guess is that the PC SharePort Utility 3.0 is not compatible with the EU dir-855?