Aborted large file transfers

[I'm posting this for a fellow in Brazil who is not familiar with the Usenet. File transfers between his desktop and laptop on his wireless network are failing.]:

Hello, My name is Gerhard Tekes, german living in Brazil and new to the group. I run a Wifi LAN using a LinkSys WRTG54 in my place and Internet acess from the Notebooks works fine, as well as exploring the shared drives, small and mid-size Filetransfers. But when I transfer a bigger file,

156MB MS-Project file for example, It starts and after +- 2-5 min of progress it says it lost the connection "Impossible to complete transfer.... The name of the file isn't available anymore".

I use a Pentium 4 PC connected by wire to the WiFi Router, using XP SP2. The Router is a LinkSys WRT54G and the Notebook is a Compaq x1100 Centrino 1,6 with Intel Wifi chipset and running as OS XP SP2 as well.

Any idea what I do wrong? I have a 2,4MHZ wireless fone as well and thought, it could be an interference, but I aleady tested with fone turned off.

Rgds from Brazil Gerhar Tekes