After a few days, there was a thunderstorm so I decided to switch off my PC.
After the storm, I switched my PC back on and formatted the disk with NTFS using Microsoft disk management.
I must say Buffalo support was pretty much useless in helping sorting out this issue. To start with, the user manual should have clearly explained all this.
I am now using the ministation and it is really great. Shame that such as great product comes with such a crappy user manual... Come on guys, if you invest all this money and time to develop such a great product, take the time it needs to write a great manual.