I have two seagate external hard drives. one is a 250 gb that works great..never had any problems. i soon ran out of room and had to purchase another hard drive which is the 500 gb freeagent desktop. since i've been using the hard drive.. whenever i want to access files i'll try to open it and it shows it's empty. so, i have to go into the disk utility to repair it and then the files are back. it's starting to get annoying. i don't even have to turn the imac off for this to happen. hours later they will just disappear by themselves. any suggestions?