For those who have had trouble with "turning on wifi" on the Transformer series thankfully there is a simple fix.
Please backup your data to external SD
Open the Settings App
Choose Backup & reset
Choose Factory Data Reset
If you are unlocked please also look at flashing a new ROM
I've had this issue and can confirm that this clears it. It's almost too simple to post but perhaps it will help the google visitor who is looking for a fix!