Sony VAIO & Vista wireless connection problems

Hi there,

I use a 3Com 3CWRDR100A-72 router that has worked faultlessly with many
devices in my house;

W2K laptop
XP Tablet PC x 2
iPAQ 2210 & Socket CF Wi-Fi card
iPAQ 4700
XBOX 360
PS3
Nevo SL
Momento Digital picture frame x 2
20+ visiting laptops etc. etc.

You get the idea ;^)

I use MAC Address filtering for security.

However I have a brand new Sony VGN-FZ21Z that will not connect wirelessly
to it...well sometimes it has but most of the time it doesn't,

I have the router set to broadcast SSID and the FZ21Z sees it OK.

With no encryption the FZ21Z will not automatically connect after coming out
of standby or being shut down.

Using WPA it has managed to connect probably 2 times out of 20 but mostly it
fails - the log reporting a timeout error.

I have a Sony VAIO VGN-N38Z sat next to it that is fine even when the SSID
is not broadcasting.

This is driving me crazy...to help my sanity and my hair can some kind soul
offer some help/advice/tips please?

--
Thanks & regards,
-pp-