iMac WiFi issue

I leave my iMac (24') on almost 24/7, putting it to sleep while not in use. Sometimes when I resume from sleep I encounter the following:

1. WiFi shows full signal
2. Loading web page in Safari loads slowly then stops
3. WiFi sometimes shows degraded signal at this point, but sometimes it doesnt
4. I disable then enable the Airport using the icon at the top of the screen
5. WiFi works as expected

Rebooting the computer fixes this issue, but it is becoming annoying. Is it a know issue, and can it be resolved?

Try to check "Disconnect when logging out" on the Advanced preferences of Airport :