I was on CM 6.1.2 and had installed a home screen app that puts several widgets on the home screen. I'm not sure if that's the problem, but when I wiped and installed MIUI 1.7, my touchscreen was completely unresponsive and I couldn't unlock my phone. I could find no way to disable that home screen app and I think it is conflicting with MIUI somehow. Either that or my touchscreen magically broke during the update.
I'm restoring to CM for now. I'm going to uninstall that app then reinstall MIUI to see if that helps. But for future reference, is there a "safe" mode that we can boot into that won't launch anything but the default apps?