Xperia sola, P, U wi-fi freeze FIX
Many of Xperia users on ICS experence an annoying bug when wi-fi hangs and doesn't turn off, unless you reset the phone, and blocks the use of 3G data. I found temporary solution until Sony fixes this permanently. In order for this to work, your device needs to be rooted, i.e. allow access to system files and folders for select applications. Google how to do it.
Heres what you need to do when rooted:
1. Install a file manager like Root Explorer or ES Explorer, both are free on Play market. I used the latter.
2. Turn off wi-fi
3. Open the explorer, go to root/data/misc/wifi and delete wpa_supplicant_bgscan.db
4. Turn on wi-fi (this will generate a new wpa_supplicant_bgscan.db file)
5. Go back to root/data/misc/wifi, select the new wpa_supplicant_bgscan.db, and change all of its permissions to "read only"
6. Enjoy your bug-free wireless!
Apparently this file accumulates data which eventually causes wi-fi to freeze, so making it unwriteable fixes the problem.