Dropping connections

I have a home wireless infrastructure setup consisting of my
desktop which is connected by a Linksys EtherFast 10/100 LAN card
to a Linksys WAG 54G Wireless-G ADSL Gateway. This gateway's DSL
router connects to my ISP with a DSL phone line. All is well
with this part of the system. It is very stable and totally
reliable 24/7.

I have a laptop which is using a Linksys Model WPC11 Wireless-B
notebook adapter.

My wife has a desktop using a Linksys WMP54G PCI adapter.

The whole setup worked very well for a few months, but the past
few weeks the laptop and my wife's desktop have been dropping the
connection and can't bring it back up. I get the message, "You
are connected to the access point, but the internet can not be
found.

(Note-this is only with my laptop and my wife's desktop
computers. My desktop computer remains connected with a very
fast, stable connection)

The signal strength reads max at both of the problem computers,
and when they are connected the setup works fine. If either
computer is left unattended for a while the connection will be
dropped and the only way I've found to bring it back alive is to
re-boot.

I have tried disabling the 64 bit WEP encryption, but got no
better results. I have looked for signs of any other wireless
networks in the area, but have never found any indications.

Can anyone offer any suggestions? I am at the end of my tether
with this set of problems.