For what it's worth, I have the same problem with a Seagate 250GB usb drive. It used to be flakey, but now it doesn't recognize the drive at all, but it shows up in system devices.
Originally, the drive was repartioned for half NTFS and half EX3(linux) At one time I installed Linux on the drive. Now when I boot up my laptop, I get a GRUB error message. Apparently the Seagate driver is looking at the boot record on the USB drive. Haven't found the answer yet.

I moved you post to another thread because your problem is not the same. There was no mention of partitions or grub errors, for example.

Also it is considered poor forum etiquette to interject your problem into someone else's thread. You are certainly welcome to participate in any thread, but new problems get new threads.

In your case, I would start by noting the error, then searching on it.