From what you tell, I believe the problem lies with the drive. The fact that the freezing spot changes, is a very good indication of it. It could be that the filesystem of the drive is corrupted or that the drive itself is damaged. Try a full format for the drive (be sure to make a back-up of any data you need) and check whether that fixes your problem. If not, try another drive and if that drive does work, then it is obviously the drive which is causing the problem.