Hellpower. What the hell?

[Soyweiser]

I was experimenting a bit with the hellpower spell. I had two skratties next to each other, casting the spell. And the first went of great. (Giving all the various bonusses and problems with hellpower). But the next one casted hellpower, got no bonuses and no fatigue, and immediately casted another spell (quicken self). So, somehow it ignored the second casting of hellpower in the same turn.

Anybody seen this before? Is there a limit on the amount of creatures you can provide hellpower to in one combat?

Ps: and just if anybody was wondering, the autogenerated horrors from the hellpower spell can also be upgraded horrors. They start out as lesser horrors. But get bigger fast. (the second combat I already saw a normal horror).
Ps: Using CBM 1.6.

Edit:
WTF, now even a single casting of hellpower failed. Odd, I think in vanilla the spell requires blood 3. So I think the spell failes because my blood 2 mages cannot cast the spell, as they cannot use the required nr of blood slaves.