We have had months of issues with intermittent loss of wi-fi and internet. Odd errors with one or both bands losing connection. Also, weird issues with security resetting to WEP and then reverting back to WPA. Here are the logs etc:
Sorry to read you are having issues with your wireless connection.
Have you tried to change the wireless channel to see if that improves the connection?
In regards to the security reverting to WEP, do you notice this within the router settings or does the device ask for this? If it is within the router can you try a factory reset (be mindful any saved settings will revert to default), and see if it happens again?