I know this may sound wierd but I have done it many times and it works.
Make sure your computer is not setup with an static IP but rather dynamic.
Turn your computer off.
Unplug the ethernet cable comming from your router to your computer,
Connect the drive directly to the computer with the ethernet cable and the turn your computer back on
After you do that wait a little bit and ope the commad promt (press the windows key and letter R on your key board and type cmd on the run prompt)
Once cmd opens up type netview and this will show you the devices on the network which in this case it should only be the NAS.
This will give you the name of the device, try pinging it (Ex. ping devicename) then hit enter
thsi will give you the IP of the device,
Try accessing it using the name or IP addresss
If there is no device listed, just open IE and type wdsharespace (I beleive this is the default name but I may be workng)
Let me know what happends