I just got SL6000 today and at first it gave the same problems , you mentioned.
Hope this helps
1. Go to the network tab and click on \"Add\"
2. Give the ESSID name as the same name you have given in the desktop pc.
3. Make sure you have ad-hoc selected in network type
4. First of all, to be sure, make wep disabled in zaurus as well as desktop pc. (If it works, then you can add wep key)
5. Give the TCP/IP address in the TCP/IP column and make sure you fill the network mask and gateway.
Here is one more step which did the trick
Open the terminal and type
cat /etc/resolv.conf
The ip address of gateway pc must be present in this file. If it is not, (which was in my case), open vi editor and
add the ip address of gateway pc.
Now, you should be able to connect well to the pc