Phone not booting after flashing Hyperion 9

I followed the steps on this link to install Hyperion 9 on my old Samsung Galaxy Y. After completing the installation and rebooting, the phone is stuck at the Samsung logo start screen. I have tried redoing the whole installation a few times, just in case, but only to get the same result. I waited for around twenty minutes at the Samsung logo each time. I previously tried two other ROMs which do take time on the first boot, but the wait (~3 minutes) is after the Samsung logo screen, i.e., at the ROM's own logo screen, and everything was fine after that. I had installed something with "EXT4" for one of the earlier ROMs. I'm not sure if this might be preventing Hyperion from starting. What could I do?