I also use Xperia S, and getting the same problem. Here's how I fix it :
You do this with 7-Zip/WinRAR
Note: DO NOT EXTRACT ROM!
In the ROM go to:
/META-INF/com/google/android/updater-script
1.) Open updater-script with a script editor such as notepad/notepad++ (makes things 10x easier), or...