www.careyholzman.com/netfixes.htm

Carey

Here are some tests to help find the problem:

1. Run the wireless network utility program on each computer and
verify that the wireless cards have actually made an ad-hoc connection
with each other.

2. Use Winipcfg to verify that the wireless cards on both computers
have IP addresses in the same subnet.  If you haven't assigned any IP
addresses, they should automatically assign themselves compatible
addresses in the 169.254.x.x range.

3. If the IP addresses are OK, try pinging each computer's IP address
from the other computer.  

4. If #3 works, try pinging each computer's name from the other
computer.

5. Go to "TCP/IP -> Wireless card" | Properties | Bindings and verify
that all of the boxes are checked.

6. Make sure that there isn't a firewall program blocking access over
the network.

If those steps don't help, un-install and re-install Client for
Microsoft Networks.