There's a similar thread about this down below, but my problem is different. It doesn't happen every time, but occasionally when waking from sleep, even though Airport shows a full strong connection to our wireless network, Firefox and Mail behave like they're offline. I've run Internet Connect to make sure the wireless connection is up and yes, it is. I've tried quitting and restarting the programs, and when that didn't work I tried restarting the machine. Still, Mail and Firefox were unable to access the network even though it was at full strength. The only thing that finally may have worked (or maybe it was a coincidence) was running Mail's Connection Doctor, in the middle of which everything went green again. What's going on here and how can I keep it from happening?