Why do I have to turn on airplane mode to connect to wifi and why do I have to turn airplane mode off to get back onto my mobile network?

[cswilson78759]

Switching between wifi and 4GLTE on Galaxy S3

My Galaxy S3 won't connect to wifi unless I first turn on airplane mode; then it connects fine. To go back to 4G I have to turn airplane mode off again.
-- I have autoswitch (wifi to 4G) turned on
-- I have the latest android update.