Windows98/XP Wireless problems.

Network consists of the following:
ADSL Wireless Router with 4 Ethernet ports
Desktop XP PRO with Wireless PCI card and Ethernet adapter
Laptop XP Pro with on-board wireless
Laptop 98SE with Ethernet adapter and Wireless PCMCIA card

Firewall (Norton Antivirus on both XP's)
Firewall Zone Alaram Pro on 98SE

DHCP enabled on ALL adapters (although it makes no
difference if I use static IP addressing)

File & Printer sharing enabled on all PC's

Problem:
a) When using wireless ONLY,i.e. NO cables attached to
Router, XP PC's can see each other AND 98SE and can browse
shared files etc.
98SE laptop CANNOT see either of the XP Pro boxes
Pinging the XP boxes times out

When the 98SE laptop is CABLE ATTACHED and Wireless IS
enabled to the Router, XP PC's function as before, BUT NOW
the 98SE box can see the XP boxes and share all files!

b) When the 98SE laptop is CABLE ATTACHED an Wireless IS
enabled to the Router, on start up of 98SE box, Error 38
(I think) is returned saying error loading protocol 1.
Computer names are UNIQUE throughout the Workgroup.

I've tried disabling 128-bit WEP, I've deinstalled Zone
Alarm an retried. I've turned off firewalls on XP,
disabled ICS, in fact everything I can think of, and I
still can't get to a true wireless environment which is
what I need when broadband finally arrives in my village.

Anyone got any clues - 'cos I don't know what to try next
Thanks
Keith