Hey guys. I've bought this external HD that works perfectly with the same cable on a MacBook, giving me USB 2.0 speeds. However, when connected to my 2.4 GHz iMac it gives me about 2mb/s, which is soooo slow. Why is this? My external HD is formatted in NTFS and I use NTFS-3G on my iMac HD, so I can transfer files more than 4GB in size. Help? Thanks!