Well not only that, but sometimes the spell icon itself is bugged also. I was in a champ spawn and was trying to keep guild mates healed, but had protection on, so i went to cast it to turn it back off..
nothing. icon didn't work. I had to delete it, go back into the spellbook and re-drag it off, and use it again to get it to work.
but protection rocks in many areas. Sure, it makes you easier to kill, but the 100% chance to cast spells in many areas is well worth it.
I like to go into champ spawns and cast earthquakes.. hard to do with protection off when everything is casting little spells at me to disrupt, or hellhounds breathing fire, or rats shooting arrows, or well, you get the idea.
I like that i can actually cast a spell in those areas without seeing the "fizzle fizzle fizzle" annoying message.