For what it is worth.
I have had a lot of issues coping files to USB 2/removable shared device using Windows 2000 and Windows XP.
The drives would usually be partitioned with NTFS and go into a sleep mode.
Even when I check the drives with smartctl and use the long test the drives go to sleep.
I had create a batch file that would write to the files some junk once a minute to ensure the drives did not go to sleep.
My rule now is never to have a share on a removable drive where writes are being made and basically do not use them as a shared device, period.
Now, only internal non removable drives are used where a shared folder is used for my systems.