Always have to locate network after ibook falls asleep

I think that this is happening because in the past I may have OK'd some request this computer asked me; possibly in regards to passwords or keychains, but whatever the reason it's a real annoyance:

Whenever I wake up the computer (even if it's been asleep for a very brief time) the wireless network connection is gone and I have to find the network again. I'm using Airport Express, ibook G4. My partner's ibook has no such issue -- and we are using the same Airport base station, network, passwords, etc.

Any suggestions, o wise mac community?

Thanks,

Fireape

I could assist a bit more if you had stated which version of OS X you're using...

Here's what to look for but it's for Snow Leopard which I know you're not running on the iBook. However, the instructions are the same for Leopard.

Open System Preferences, Network. Highlight Airport and click on the Advanced tab. Click on the Airport tab if it's not showing... look down in the dialog box and make sure you do not have a check mark in the box that states "disconnect when logging out". This will sometimes turn off the connection when the machine goes to sleep.

If that's not the problem, it's possible you could have a failing or intermittent Airport card in the iBook.

Regards.