Using firewire 800 can't backup or transmit mass data

I use firewire 800 to connect my mbp and WD mybook studio 1G.

Every time I backup data or transmit mass data, it can work at first, but it will lost connection in a while…

then my PC can’t recognize the WD harddisck until restart my computer.

(but if I just copy small size or few files to WD hard-disc, it works well)

MBP: Mac OS/ Windows 7

WD mybook studio: NFS 400G, NTFS 600G

Please help me :cry:

The best advise for you is to check the Energy Saver (Mac) setting or Power Management on Win7 (PC).

Make sure that the Hard disk drive is stays on or always on, long enough to finish copying the large file before it’s going to sleep.