Few wireless problems.

I have setup a small network with a Buffalo wireless router, used just as an
access point. NO DHCP set on this as I have a hard wired router downstream
connected to my broadband which handles DHCP.
Two PCs connect to it.
I desktop with a linksys USB adaptor and a new HP laptop with built in
wireless (make unknown).
The problems I am having are that if either PC goes into suspend or
hibernate it looses the wireless connection on waking up - it can see the
wirelees network but seems to be unable to resolve the ip address again. I
can only reconnect by running 'repair connection'.
I also find on occassions that one or other of the PCs cannot connect at all
even from a fresh boot. I just does not detect the wireless connection at
all.
Both are running XP Home and have the WPA encryption patch installed which
is the security I am using.. I have set Network authentication as wpa-psk
and encryption as aes, as per an article I read on wireless security.
The access point has the SSID hidden so the PCs are presett to connect to a
specific SSID etc.

Any thoughts on why I loose connection on going into power save and on boot
up sometimes?
As a test I gave one PC a fixed IP address and this improved things a bit
but did not cure it.
The access point is in the same room as both PCs and signal strength is 100%


Thanks
Andrew