I solved the problem without resetting my phone to its factory settings by proceeding in two steps:
1. I uninstalled Boost+. I read somewhere that the application created some conflicts that prevented the phone from booting.
I just wanted to install this, as it worked perfectly fine before an update I got on my HTC One, but now, when I try to install it, it doesn't work at all. I tried the "manual" way, with the
mv hosts /data/data
ln -s /data/d...