wifi networks knocking off connections in small office

I have a office I service where they wanted to use their XP Pro laptops to
connect the Win2003 server via wifi. The problem is when other near by
offices lights up their wifi on another channel (1 or 6, office is only one
on 11) with encryption, the server get the notification of "one ormore new
network" and also looses it connection to the clients.

The server is already set to only look at the local office AP only and
infrastructure AP's only. The office ip structure is not standard, so it's
not the same as others in the building.

The XP laptops only loose the local AP signal when the message on the other
businesses AP's go active annoucing their presents. What can I do to reduce
or stop this from happening on the server or XP Pro clients (I think they are
all SP1 but still fully updated to that point) Idea's....

Thanks