Attention: This method will completely wipe your phone!!!
You can find the reworked Tutorial here: http://android-tutorials.org/
Video of the first step is online: Step 1
Video of the 3 & 4 step is online: Step 3 & 4
If you have problems while re-rooting or custom recovery (unrevoke) try to downgrade again with the above procedure.
Make sure you have made a new goldcard.
If you have problems e.g. 140 ERROR please follow these instructions (thx to raz2133)
This will fix your MISC Partition so you can flash back original RUU files.
P.S. i hope you can understand this because english is not my foreign language