I have a 2.4 Ghz MacBook that i bought last summer, and a 250 GB Western Digital external hard drive (powered by computer) that i also bought last summer. My problem is that My computer will not recognize the hard drive at all. it doesn't show up anywhere, and after attempting to reconnect it over and over, it will eventually pop up, and then disappear, saying that it was improperly ejected. when i plug it into another computer, it works just fine (for the most part), leading me to believe that it is an issue with my computer and not the HD. I tried resetting the PRAM as well as the SMC, to no avail. any advice? thanks.