I can't imagine this is a new problem... I've never found anything, others haven't encountered, lol. I tend to be very lucky and have VERY little issues with this game, but let's see on this one... So everything has worked flawlessly, as this is like my 12th/13th time through ToEEE, I LOVVVVVVVVVVE 5.5, and feel it is so near perfect, everyone that mods on here, is amazing. I don't use console, and have had NO problems. But I'm now on the 3rd level of the Temple... done evey other quest... had no problems till I killed Smigmal, and then went to Falrinth... I could no longer cast spells, either my cleric OR my sorcerer. The lay on hands still works with my Paladin, but no other spells with the 2 listed. Nor will a potion of "cure light wounds" work. Basically it appears to be a miscast, but with no text, and nothing in the rolls menu. I'm not sure if it's a bug, or what... but I'm unfortunately going to have to abandon this party of 3 it appears, because even with multiple rests, and travelling to other areas, I still cannot cast spells :-( Hopefully I'm doing something stupid... hope someone can help!
Hmm, it's an effect from the Globe of Invulnerability that Falrinth casts. It technically shouldn't last that long. Try Jaroo's Spell Permanency fix.
