Asus issued an update v220.127.116.11 that brought Ice Cream Sandwich operating system to Transformer TF101 first in Taiwan, and later worldwide. Unfortunately for Asus it didnt go so well as customers who rushed to upgrade to Android 4.0 immediately reported random weird reboots and other problems.
Yesterday Asus started rolling in the US a new maintenance software update version 18.104.22.168 to fix what *.11 broke (random resets, unstable WiFi connection and more).
The update is available OTA (over the air) and apparently breaks the root privileges.
Folks over at XDA forums found alternative way to keep root privileges after upgrading to the latest version. For instructions head over to XDA thread here.