Xperia Play (R800a) stuck at Sony Ericcson logo on boot

OK then: Recently, the Xperia Play's screen has been broke. I just put in the new flex cable and THAT seems to work... except now: 1. I can only start the phone on USB power, otherwise it freezes at the splash. 2. If it boots, the touch screen doesn't work. As I can't unlock it without a touchscreen, I couldn't test it. I did tighten the digitizer cable after this, no dice. This link seems to describe my symptoms well.