Wierd Vista Access point problem

I have a Netgear WNR854T router set to N for use with my Macbook Pro -
works great with a 144mb connection.

Attached to one of the LAN ports or the router is a Edimax 54mb access
point also works great......

I use the 54mb so a Vista Home Premium laptop (b/g) can get access
without using my N network (or having to switch it to b/g).

I have tried everything to make the Vista machine log on to the 54mb AP
automatically - sure the Vista machine see both, but even though I have
set it up to log on to the 54mb point, it always tries to connect to the
N network - failing.

I then have to connect the Vista machine manually to the 54mb AP and it
works ok.

I was already considering removing Vista and putting XP Pro on the
Laptop (it was bought new with Vista on it) - because IMHO I think Vista
is not worth the hassle - so does my wife who's laptop it is.

Does anyone have any ides why it would do this, or is this just another
Vista 'bug'

Clive