Buffalo DriveStation broke down

My Buffalo DriveStation (HD-HB250U2) was not working. My iMac did not recognize it nor show anything on the hardware list. My Buffalo LinkStation could recognize a USB drive but could not show the details of it. I said to myself, may be I need to buy a replacement because the DriveStation is the primary backup of my iMac. And it was close to full capacity. Therefore, a replacement has to have 400 or 500 GB, which cost HK$1400.

But I need to figure out which part is broken, whether the hard disk is broken or the main board of the USB drive. I borrowed a USB-to-IDE cable from office, remove the hard disk from the DriveStation iron frame. The hard disk is a Western Digital one (WD2500BB, 250 GB, ATA-100, 2 MB cache). If the WD failed, I may purchase another ATA HD, instead of buying another DriveStation.

The WD start up noise seems very okay. But it still not recognized by iMac. I changed the jumper settings from "Master alone" to "Master with Slave present" and try again. After a while, it appears on the desktop. All content were there and looked just fine. So, the WD is okay. I undo the jumper settings and try the DriveStation again. Nothing happens. I changed the jumper to "Master with Slave present" and try again. It took a while but finally appears on my Mac.

Isn't that strange?

p.s. seems that Buffalo's quality was... sigh (see user reviews)