Linksys Wireless-G WAG54G S.O.S.

I have a Linksys Wireless-G WAG54G ADSL Gateway with a Dell D610 Laptop
connected via a wireless network. The operating system is Windows XP.
All OS and firmware updates have been applied. The Gateway is situated
in a good position for transmission. The Laptop connection always shows
good to excellent signal.

The connection to the Laptop is often lost. When this happens, a repair
connection doesn't work and the network disappears from the available
networks list. Refreshing the list doesn't make the connection
re-appear. A few networks from neighbours are still visible though.
Even a reboot of the Laptop doesn't re-establish the connection. The
only way to get things working again is to reboot the Gateway.

What do I have to do to establish a more permanent connection?