Sk17i bricked?

[Webster2703]

I need help with my SK17i, because I may have bricked it. The last ROM I installed was the Xperia Project cyanogenmod. It worked fine but I wanted to go to stock. I tried installing this: http://forum.xda-developers.com/showthread.php?t=2251685 with my CWM Recovery but after that it didnt start. After the start it shows the Xperia Project logo and then only a black screen. I can however get in the Recovery and Fastboot mode. The Sony Emma programm doesnt recognise the phone, so I dont really know what to do now. I'm a beginner but my guess is that the phone has the old wrong boot img and thats why the installed Stock ROM isnt booting. Maybe someone can help?