i dont know if this is board-specific problem, but i had the same problem with my new hp laptop. Once i transfer multiple movies to my esata hdd, it gets disconnected after about 10minutes.
i found this solution from another forum.
right click on your esata drive (actually, any drive is fine)
go to HARDWARE tab
select your esata drive
go to POLICIES tab
UNTICK: enable write caching on the device
although there is a risk of data loss when power fails, its your choice...
but this solved my own problem, i can now copy any amount of files on my esata drive.