Quoting Derek Paxton, reply 3
Fix has been streamed. You will need to start a new game for the change to take effect.
I might be damn nosy, but I want to know what happened
I applied the latest patch to my public version of the game before I made the streaming patch for splash damage. When I did that I noticed the spell file didn't get updated (it was way out of date). I had the guy that builds our installs check out why the patch didn't update my spell file. While he was troubleshooting he made a backup copy of my spell file.
After he figured out the patch issues I created the updated streaming file to fix the splash damage problem and posted it on the site. Because there was 2 spell files in my directory spells were in the game twice. Though the game usually merges redundant information, mana costs were being applied from both spells (ie: you paid 5 mana for the first instance of the inspiration spell, then 5 mana for the second).
The fix took finding and deleting the backup corespells.xml file, rebuilding the streaming file and posting it on the site.