if you click really fast on a monster, you can hit them multiple times with this spell. then they only get one turn for your five. i thought it might have been the animation speed (i usually play with it +1), but it still works on the default speed, although you can only get two or three in. it does properly use up your mana whenever this happens. looks like it also only happens if the enemy is not in melee range. only exception is if you're a vegan and the monster is an animal that doesn't normally attack you.
I saw this too, it happens on a lot of spells. I'm pretty sure you can do this with Pyrokinetic too. I'm on OS X, Snow Leopard, so it seems the problem isn't linked to the OS.
I feel kind of bad for exploiting this bug now. I used it to clear out a mysterious portal. I mean, sure, i did have Love Will Teleport Us Apart and Thaumaturgic Tap, so I could have done it more slowly. But monsters might have spawned and made it harder in the time that would have taken. brb enjoying my awesome new items >_>
Just try putting four Fleshbores on a single monster in one turn, and laugh maniacally as his skin falls appart.