Local ISP has resources for share. Ethernet cable plugged into US Robotics 8054. Everything works well until a big download (eg.500-600 Mbytes) is downloaded. When it happens, wireless speed decreases smoothly to the minimum till it drops. No other clients using the router. No other wireless stations around. Client PC is a fresh Windows XP installation. When plugged directly to LAN - download goes OK without interruptions. Router has latest firmware possible on manufacturer site.
Router is in G-only, Turbo mode.