A friend gave me his OLPC and I received it gratefully
He had an old OS (not sure what version it was). No network connectivity to secure wireless. I poked around and was ready to shut it down and give it back to the friend. But the laptop was too cute to giveup. So started searching aroubd the web.
Summary of what I did :
1. Used a USB stick to update to the latest stable version of OS : Build 802.
2. Then started a long nightmare of diggin into stuff I usually avoid. I have a 2Wire modem. From browser type//home and go to the router settings. Go to HOme Network Tab and under it - wireless tab. Get your router settings - Network Name (SSID), Authentication (mine was WEP-open), Channel (mine was 6) . Wireless mode on mine was mixed and I changed it 802.11g.
3. If you are using default encryption key , then the 10 digit id between square brackets  on the underside of your router is the encryption key. If it is custom, then you should remember the key or if you forgot, please ask for a reset from your service provider.
4. Go to the neighborhood view and select the circle with the SSID that is your router SSID. The enterpassphrase window will appear. Select 40/128 Hex and then enter the 10 digit number from under the router. This is the 40/128 hex number. Click OK.
I was connected.
Hoe it helps.