okay, i haven't booted up my incredible in nearly a month but i think the reason that clockwork wouldn't take your PB31IMG is because it needs to be installed through hboot which is what you initially load into when you hold vol down and power. it will say something like checking so and so IMGs and go through a search for a list of different zip files. the PB31IMG.zip goes in the root of your sdcard but it won't be recognized by hboot unless the sdcard is formatted as fat32 which is why i thought i had the wrong image whenever i tried to update the radio.