Yesterday I flashed CM 12.1 on my Galaxy S2 gt-i9100. I rooted the device by flashing Siyah kernel via Odin. Then using cwm based siyah recovery I did the factory reset and wipe cache & dalvik and flashed CM. Everything went fine and my phone booted into CM. However, when I powered off the phone, and switched it on again, its stuck at the Samsung Galaxy S2 screen. I've been thinking but couldn't figure it out. Help is very much appreciated.