Troubleshooting

As long as the WiFi-cards can 'see' each other directly with their radios, doing a ping will work whether olsrd is running or not. This works because the large netmasks effectively make every node link-local, so routing issues are sidestepped at the first hop. This should be checked first if things do not seem to work as expected. Most headaches people face with WiFi in Ad-Hoc mode are caused by the fact that the ad-hoc mode in drivers and cards are implemented sloppily. If it is not possible to ping nodes directly when they are in range it is most likely a card/driver issue, or your network settings are wrong.

If the machines can ping each other, but olsrd doesn't find routes, then the IP-addresses, netmask and broadcast address should be checked.

Are you running a firewall? Make sure it doesn't block UDP port 698.

Have fun!