mac airport propblem..

I'm using a friend's ibook, but recently I've begun having problems with connecting to the wireless network. Everytime the computer goes to sleep, it disconnects from the network. When you try to get back on, it can't find the network, and won't connect. If you restart the computer, it has no problem finding the network and works fine - until you let it go to sleep again.

Any ideas on how to neutralize this situation?

Win XP has a "Repair" option - does Mac have anything similar?

If not, try disabling it and re-enable and try to reconnect.