There have been some issues with mana, indeed. But this one can have an explanation, at least when you say you can\'t cast at 100% (I\'ve no explanation for that weird draining that you experience, and I think I read about somewhere else too.)
Unfortunately, now there\'s no information of the total (absolute number) amount of mana you\'ve, so, what I\'m going to say it\'s just a guess of what _could_ be the reason for you not casting spells.
If you take a look to your char mental stats, you\'ll realize that they\'re poor, that means that his/her mana points are too. What could be happening is that your char, indeed hasn\'t enough mana points to even cast a simple spell once, so, the fact that it\'s at 100% doesn\'t matter at all. If I remember correctly, training 3 levels up on mental stats (either int, will or char) should give you one extra point in mana.
If you feel with enough will as to try it out, you\'d be training a bit your charisma, for instance, and see if you reach a point where you can cast a spell. Still, I\'ve to warn you, there have been cases where mana training is bugged, that is, the stats get increased, but that doesn\'t reflect in the total amount of mana your char has; again, since the number won\'t be visible for you, you\'ll be making sort of a blind training that, eventually, can allow you to cast a spell.
