Bank error in your favor?

[garzahd]

I just returned to the game after taking a break for a couple months. Started up a mage on impossible, who is currently beginning to work on the freedom isles.

Twice in the past hour, my max mana has increased by 30 for some unknown reason. I didn't see any unusual popup messages, but I can't easily repeat whatever it was that happened because by the time I notice, all three quicksaves have already been saved over.

Needless to say, a mage with 131 mana plays a whole lot differently from a mage with 71 mana. Anyone know what causes this? Is it a bug? It's certainly nice having the extra mana, but I feel sort of guilty.