All of the sudden my MacBook doesn't connect to my wireless after waking from sleep. My network shows up at full signal strength and it remembers the password correctly, but I get an error message when I try to connect from the menu bar. The only way I can get on the internet is to go through Network Diagnostics and turn it on there. I don't understand why it works every time through Network Diagnostics and never on it's own or through the airport menu bar.

Nothing has been changed or installed or reset on my computer that I know of. Restarting doesn't fix it, nor does turning off the airport card. Any ideas?