okay--I am here now...I understand your buffalo external HD isn't working correctly...and disc first aid won't do anything. You could try TechTool Pro, a demo for that is free. I hope you have your stuff on that HD backed up somewhere else, or that it's not crucial. maybe you could reformat it or try Drive Genius or another program. usually if this kind of thing happens it shows you have a problem . Worst case ( I don't want to scare you on this one) it may be that the drive itself could have failed. you could try DriveDX. or discDrill (cleverfiles.com) I have no experience with any of the latter program, only TechTool Pro (which can be useful) and Data Rescue 3 (which works to recover all data off of a hard drive and costs around $100)
maybe it's the drive's enclosure
sorry I can't help you more... I'm no expert...hard drives can and do fail usually without warning.....
john B