Do you have a link to your external HDD?
Control Panel/Administrative tools/computer management/disk management and check out the status, is it NTFS, and healthy?
If you're using an USB hub connect it directly to the PC's connectors, try both in the front and back. Try another usb cord. Try the HDD on some other machine.
I have tried it on all of my USB ports with and without the USB cable. I normally use my hub ports because the PC ports are not hi-speed. I get the same results. I also tried the Admin Tools diagnostics. It shows uip as a 55.89 G (100% free and unused) drive when it is actually 60 G. The Status inicator is "healthy" , but there is no file system listed. I have not been able to try it on another machine yet.