How do I progress in Ars Magica 2?
Solution 1:
Alternatively, you can stop casting the spell at a higher caster ability. Press the C button to lower the mana cost (and also the effectiveness, but it's worth it).
Solution 2:
it looks like I found my anwer here: http://www.minecraftforum.net/topic/2028696-ars-magica-2-162164-version-102b-updated-oct-27/page__st__1880#entry27039682
the /respec command should does the trick. I tried it out and speced to projectile, phsical. Now I can cast the spell and gained several level.