Hello,
I did also buy a wl-500gp in feb. and did upgrade from asus firmware version 1.7.6.9 to 1.9.7.2.
After the upgrade I did offen loose connection to the USB port used for a storage ( in my case a USB stick).
The tcp/ip connection to the internet and also to the router were very bad. Between 5 and 10 % packages loss.
Did then downgrade to version 1.9.7.0 and it is working perfect.
I have connected a USB printer, USB stick, two on LAN and two on WLAN. I am using the download master, FTP and SAMBA share
/fsmik