From what you're describing it's pretty certain that either the read/write heads have failed or the firmware inside the drive has become corrupted. It's very common with this model that just one read/write head will fail causing the drive to either not click or only sporadically click when the buffer hits a certain LBA address. Sometimes they can get a firmware issue related to the auto reallocation functions which make the drive respond so slowly that the system will give up before it can load the SmartWare.
In any event, the only real option, if you need the data back, will be professional recovery. The good news is that these drives are almost always recoverable. Out of the thousand or so we've done here, only a couple couldn't be recovered. If you let me know where you're located I can probably recommend a good company to use that's not too far away.