Lewis:
A few questions to narrow things down ...
To make sure ... Are you using the FREE version (NASLite) or NASLite+ ? ( I had some WindowsXP issues on the Free version which went away after buying NASLite+USB. )
Have you looked at SYSTEM log ("System.htm") ? Check to see if there are any "errors", "dropped", "overruns" or "frame" in the lines that start with "RX packets" or "TX packets" at the bottom of the log.
Also, look at your NMB_Log and SMB_Log's and if there's anything unusual there, post it here.
What are you using as an ethernert controller ?
Does the HDD SMART status look normal ?
Does the connection get dropped when you copy the file back to the PC ?
Georg