AirPort connection problem on iMac after waking up

I have two iMacs. One runs Tiger (4.11) and is connected to a D-Link router via cable. The other runs Leopard and connects via Airport. They have been running fine for 2 months.

I'll call them wired-Tiger and wireless-Leopard.

Last weekend, I connected to the wireless-Leopard from the wired-Tiger in order to drop some files in a Public Folder (file transfer between machines). I have done this before a few times, never an issue.

Since then, whenever the wireless-Leopard goes to sleep or is put to sleep, it does not connect to the web when it wakes up, if the wired-Tiger is also asleep.

The wireless-Leopard appears to be connected via Airport, no errors reported, but no email or web access is available. While in this state, if I go the wired-Tiger, hit a key to wake it up, the wireless-Leopard then gets its web connection back. I can then put the wired-Tiger back to sleep and the wireless-Leopard will continue to work.

Have I got some setting wrong in the network share?

Thanks.

Just an update. I downloaded new Airport drivers (bundled with Time Machine stuff that I don't use) and the problem went away, for the moment at least.