I have a MacBook Pro with it dual-booting with Ubuntu 14.04 and Mac OS X, and a few days ago I upgraded Ubuntu from 13.10 to 14.04. When I suspend and then resume the system, wireless tries to connect but fails, and I tried some solutions like restart the network or remove and reload the WiFi kernel module (b43), but nothing worked. Only a restart of the system solve the issue.

The output of dmesg indicates an authentication problem:

...

[ 8050.906223] wlan0: deauthenticating from <mac_address> by local choice (reason=3)

[ 8050.914824] wlan0: authenticate with <mac_address>

[ 8050.915142] wlan0: send auth to <mac_address> (try 1/3)

[ 8050.917960] wlan0: authenticated

[ 8055.919691] wlan0: deauthenticating from <mac_address> by local choice (reason=3)

[ 8066.438256] wlan0: authenticate with <mac_address>

[ 8066.438631] wlan0: send auth to <mac_address> (try 1/3)

[ 8066.440185] wlan0: authenticated

[ 8071.447980] wlan0: deauthenticating from <mac_address> by local choice (reason=3)

[ 8082.466500] wlan0: authenticate with <mac_address>

[ 8082.473305] wlan0: send auth to <mac_address> (try 1/3)

[ 8082.493654] wlan0: authenticated

...