Not really a 'technical' issue, but rather a game system that the UI fails to explain.
While I realise the game is created for fans of Infiity Engine games, and there are certain things that players of those games take for granted, it took me a while to figure out that wizards and priests were limited by how many spells they could cast between rests. Prior to that I assumed it worked similar to 4th ed DnD, and had a bit of a rude awakening and confusion when I discovered I couldn't cast any spells in the middle of a fight - and even longer to find where in the UI it told me how many spells I had left.
I've heard similar things from friends whose frame of reference was WoW, and were expecting a cooldown on their spells. Given how exhastive the rest of the game system are described, I'm suprised at this oversight. Having reminder text in the spells that only a certain number of spells can be cast between rests would be a significant help for new players.
