usb wireless network adapter goes to sleep :(

I have a Linksys usb wireless network adapter (wusb54gs) on a XP Pro
system that works great until I leave the computer for a long time.
After a long period of time, not sure exactly, but like over an hour,
the adapter stops being connected to the internet and my downloads
stop.

I went into power management and made sure *nothing* shuts down or
goes into standby, but still this happens. I do have APM enabled, but
nothing set to shut off. The only thing really active is the screen
saver, but that comes on and I can still break out of it with internet
intact.

Is there something in the bios that could be putting the usb in sleep
mode? or maybe just a characteristic of usb wireless network adapters?
Is there a way to keep it 'alive'?

thanks for any help/input,
Patrick