I rooted my att GS2 using Zedomax's guide and install Ultimatum ICS ROM using his guide then decided to go back to stock because of the lag on the browser and getting ready for the official ICS update from ATT, I followed his guide on unrooting the phone, it went well and I got it back to 2.3.4 but I want to update to 2.3.6 just for the sake of updating it and also my phone keeps on rebooting after I unroot it, but when I try the OTA update, it completed the download but when it try to install it stops at 37% and say "update fail". What do you guys think?