Unable to open files on the WD drive

I have a 2T external drive (mybookworld) attached to my router. It has worked fine but recently I cannot open it from my PC. Sometimes it shows in my network places and sometimes it does not but either way, it will not open. When I ping it, it responds, however.

Hello, I will recommend you to reset the drive by pressing the reset button in the back of the unit for 4 seconds, you might also want to change the drive ethernet cable and change it from ethernet por in the router.